So if you can't control which airline you fly, how is attaining status (and planning your travel accordingly) that will allow you upgrades anything close to remotely possible? You're basically at the mercy of the luck of the draw, right?

For that matter, upgrades that are useful for longhaul are only going to show up if you fly a LOT within *A- 100,000 miles (and a lot of deep-discount Y fares by non-US carriers like LH or SQ won't help with those as much as UA's will- often those deep discount fares on a non-US carrier only credit at 50%, or even 0%). Do you project that you will be doing that much flying?

I'd probably be looking at programs that were most favorable in terms of mileage accumulation (credit card, RDM bonuses) first and foremost, because that's really the only thing you're likely to get out of the deal if you have no ability to preferentially choose a carrier to maximize status- large piles of miles that you can redeem to fly in something other than Y. That probably means that your choices are US and CO/UA, realistically. (The problem with BMI DC is that if it's assimilated into the LH Borg collective after 2011... well, LH M&M would be a terrible program for you. High award costs, fuel surcharges, high mileage thresholds to gain status unless you fly a lot, not much love for deep discount Y. The only upside I can think of to M&M is that if you were willing to pay a significant mileage premium, you'd have access to SQ award inventory nobody else in *A has, outside of SQ KF members, which would be handy flying out of SIN/CGK.)