Going down the list:
Option 1 seems messy and, if I'm looking at the geopolitical map, could trigger some sort of explosion. If BA were to decide to essentially throw Americans out of their main loyalty program, I would not be surprised to see government retaliation of some sort.

Option 2 doesn't require "two classes of miles" - you could just tinker with the relative earning rates. The issue is that if "consumer miles" are essentially devalued too far (at least, relative to the competition), credit card spend is likely to go POOF! very quickly.

Option 3 runs into the fact that a lot of airlines have made it easy to spend your way to status (AA and DL are basically a blank check here), but it might be worth considering for some things. I think you'd need to ease up on some of those fees, however.

Finally, Option 4 looks like a complete mess. I would compare it to the Panera loyalty program (heck if I remember the name) that I ripped up my membership in years ago because the rewards were erratic (e.g. randomly offering free coffee for a month - I don't generally drink coffee except after dinner - or free/cheap baked goods that I never really wanted). Maybe you offer me something I want, maybe not. If so, this might be great, but if not...not.

Like, the Maldives sounds nice, but it's also...not really on my list. But say I want to go to Japan, or Australia, or even Disney World? (Note that I'm US-based, so my map changes a bit here vs someone in London...but the point remains and this is WLOG.) Also, there's the question of relative valuation of that one-shot award ticket versus what you're earning on points now - that could line up either way. The bottom line is that a lot of this is based on questions of taste (and potentially alignments of folks' other loyalty participation).

A couple of thoughts come to mind:
(1) Offer straight discounts based on reaching some threshold (or one of a few thresholds). AA and DL both give 11 miles per dollar spent at their top tier statuses (EXP/CK and Diamond/360, respectively). It wouldn't be hard to, say, convert that into a 15% discount on flights (though you might need to fiddle around the edges to make sure that someone spending $20k this year for Status X doesn't get knocked out next year because of the discount - that'd just get awkward - but a number of programs seem to be addressing that by bonusing spend towards loyalty status for upper-tier members, so compensating in that way wouldn't be too hard.

(2) Offer a broader suite of options. Again - I decline the Maldives because that's just not on my list. Maybe I don't like the beach? Anyhow, if you offered someone from London the choice of the Maldives or 3-4 other choices (let's say...Maldives or Canada for free, Australia/New Zealand at a deep discount [but not free]), that starts looking a lot better than the airline trying to just decide where I want to go on vacation for me.

(3) The airline probably needs to do something to address the question of "excess spend". If I don't know what gets me the flight to the Maldives, I'm likely to treat it as a bloody mirage much like I treat CK/360. If I do know what gets me that flight, then I have a target...but if the target is $20k in spend, what do I do if I'm looking at $30-40k in spend? (At the same time, I'd point out that if I get offered the Maldives for $20k and someone else gets offered the same trip for $40k and we both post on here, that $40k guy is gonna feel hosed.)

(4) There's also just letting folks "buy" status. Hear me out - points earning on BA is somewhat useless (the fees on awards alone screw the program) and I've only been crediting to BA to get OWE and Flagship Lounge access in the US. But if I could convert BA RDMs into status points (and thereby get closer to lounge access), I might just choose to do that. I know this is contra some of the objectives of the overhaul, but if all the other stuff on offer is just a goofy batch of non-sequiturs for me, being able to "buy" my way back into the nicer lounges becomes a reasonable option.

(5) Finally, it might be worth looking into more reasonably-priced redemption options outside of the airline. Look, most of the non-airline redemption options suck in terms of valuation. Yeah, I know we're all a bit weird here insofar as we focus on value maximization, but when you have an "internal" redemption value of around 1.5c and an "external" redemption value of half of that (or worse), that's bordering on "go home, you're drunk" territory.