The only catch: 30 nights is about the worst possible frequency to make Marriott your primary chain. That puts you right on the high end of Silver (ongoing), which is a lame status. (They won't let you challenge every year, I don't think.)

It's 35 actual paid room-nights to hit Gold - if you have the "new" MR Visa - stays don't matter and awards don't count.

Certainly understand the desire to diversify to increase your award destination selection. The other catch with Marriott is that the program is a bit weak on the small awards.

I'd be hesitant to leave a nice HH Diamond situation unless I felt like I could (a) sustain MR Gold at a minimum, (b) open a new MR Visa account with a U.S. address or in a market where the card has similar perks, and (c) make a run up to about 250k-270k Marriott points.

For full-service hotels, with the new Visa, it's 17 to 18 points per dollar, depending on status. Add in a Megabonus, the credit card sign-up bonus, maybe a few other promos here and there, and you're looking at about 14-15 months of your normal stay activity to reach 250k MR, which is good for one Category 6 Travel Package. 270k gets you a Cat 7 - which is any hotel in the system. (Unless there are exclusions I don't know about.)

Are you thinking of any specific award destination in particular? Perhaps folks here can provide feedback as to whether there really are good Marriotts there.