I have a a few good ones.

New appeal of cheap nights for status
1. For current status, it reduces the level of immediately bought status that can be attained cheaply to Gold. With the personal/business Marriott cards, you get 15 nights. The first meeting getting 10 nights pushes you to new gold (25 night qualification level). Limiting this to 10 elite nights only for the first eligible meeting per year would make it harder to earn status beyond gold (more appealing).

2. For current status, it's still possible to use rewarding events to "buy up" to the 50 night level or 75 night level if your credit card + actual stay activity remains just short of the 50/75 night threshold (and the SNAs/choice benefit granted hitting those levels in a year), but if you're 11 or more nights short - meeting only gets you somewhat closer, not a cheap way to mass accrue all the nights. Changing it in the merged program would reduce the buyup.

3. For lifetime status, meeting nights become a lot more appealing (if Rewarding Events is not modified) in a couple regards.
a. For many of us on corporate discount rates, especially on the non-coastal parts of the US, our average stay before taxes can be quite low, and thus we're fine on nights but short on points. Meeting nights add the nights cheaply, but offer few points (3 in old rewarding events/$, reduced to 2pts/$ August 18th) which means that you have to have a higher average room cost (and at higher end properties, other incidentals that qualify as "eligible spend", but not taxes/fees). Under the post-Aug 18th merged program, points no longer count, only lifetime nights and years at the given status you're seeking lifetime at or higher. So at that point, it doesn't matter if a night is acquired for $7/night in a bogus meeting or $300/night at a hotel. For lifetime qualification under new rules, any night is a night.

b. For those of us who are more upscale, maybe less on discounted rates, or just staying in more expensive areas like the Bay Area or Cali where a CY can run $300+/night (much less higher end properties), you can hit the points target (old LT criteria in MR) before the 500/750 nights. Not a big sweat for lifetime if you're still traveling. Now with August 18th looming, lifetime status will become harder compared to existing tiers (Old was 500 nights/1.6M points for lifetime @ 50 night annual qualification level, new program is 600 nights plus 10 years at the 50 night or more level) and another level is becoming impossible to earn (75 night level used to be 750 nights/2M points for lifetime, qualification for that won't be gone before the end of 2018). A bunch of people on FT in this group are buying up cheap nights for this express purpose (discussed in this other thread). Marriott doesn't want to tick people off too badly by just pulling off the rule changes in advance, and since the elite tiers are changing Aug 18th + single loyalty program, making any change to rewarding events earn structure just makes sense to do together on the 18th (personal opinion).

c. With the new requirement to get lifetime 50 night status (old Gold/new plat) also incorporating the ten years at 50 night clause, meeting bookings become a lot more appealing as a way to tick the box of another year at the 50 night status. I earned LTP this year, and most of my stay activity (200+ nights/yr thanks to rollover nights counting twice) was 2013-2015 (I only joined MR in mid-2012). I would not have renewed Gold (50 nights) without rollover in 2016 or 2017. Under the old program that didn't matter, because years at status didn't matter for lifetime status, thus busier years offset less busy years. If I had to earn lifetime status under the new rules, I would only have five years. That would make use of meetings to supplement actual stay activity (If any) a lot more appealing.

d. The elimination of stay based elite qualification for SPG elites in the merged program makes meetings more attractive to make up the difference.

Other ways earning nights in the current/merging program has become harder:
My personal opinion is that anyone thinking that anything beyond the first meeting earning 10 nights is being extremely optimistic. though The general direction of both companies has been to reward spend/stay activity more and tighten many of the "loopholes" for elite qualification in the program merger.

1. Marriott awarded points for multiple hotel rooms booked, but only 1 EQN per night for the elite member who booked the room, regardless of how many rooms they booked simultaneously. SPG gave the elite booking the room elite qualifying nights for up to three rooms at the same time. The less generous policy (MR) prevails in the merger.
2. Marriott offers an acquisition deal to SPG and the shareholders approve it in April 2016. Then both sides start working on figuring out what a merged program will look like. By 2017 they realize how generous the rollover nights are for the busiest elites, because rollover nights counted twice for lifetime qualification: once in the year they were earned, and once in the year they were rolled over to. MR kills rollover nights in 2017 (excess nights from 2017 will roll over to 2018, but no nights from 2018 or other future years will roll over to the next year).
3. Marriott gave 10 meeting nights flat for rewarding events regardless of the duration of the meeting (5 days of the same meeting was the same as 30 minute meetings, the posting of the 10 nights was by the contract for the room - same contract, no more nights) and regardless of whether or not one person showed up without booking a room at the hotel in a small room or if the meeting brought in 150+ people into a very large and expensive meeting room who each stayed three nights (450 room nights booked driven by the meeting). SPG Pro only gave elite nights to the qualifying planner if they drove at least 20 nights of related room bookings, and then it gave 1 elite night to the planner for every 20 nights of related room bookings, up to 20 elite qualifying nights (400 room nights / 20 room nights to get an elite qualifying night for the planner = 20 elite nights for the planner.
4. Marriott kept the 15 night bonus but limited it to one per member per year regardless of whether or not they had cards, and effectively kneecapped the Chase personal visa by making a product conversion/upgrade to continue getting the category 5 (now 35,000 point) cert, and having to drop the old card that gave one elite night/$3,000 moved across the card to get that (also, the new card earning more pts/$, generally higher redemption rates, etc.)

The old Rewarding Events program page said that you'd earn silver after your first meeting (true, as silver was 10 nights) and that each meeting earned 10 nights.
The new Rewarding Events program page on members.marriott.com says you'll earn ten elite nights after your first meeting, and then 1 elite night per 20 hotel room nights on the contract (basically copying SPG Pro).

It is technically true that the T&C could permit ten nights for the second and subsequent meetings once released, but given how much more appealing nights from Rewarding Events in the current structure becomes under the merged program for current/lifetime qualification AND the reduction of the other ways to get nights cheaply/as a byproduct of non-room spend (per above).. doubtful.

Also, the related room bookings 1 elite night/20 related room nights on the contract would become pretty pointless if you continued to earn 10 elite nights on every meeting booked anyways. Just book a bunch of smaller meetings and you'll earn the status faster/easier/cheaper than trying to drive a larger number of actual events with people staying in rooms...