I think the FA24 has a much less aggressive tune and lower boost pressure than the FA20 - the specific power is substantially lower. I assume they wanted the whole system to be less stressed due to the different market segment, as well as the tow rating requirements than an Ascent has that a WRX doesn't.
While I would rather have a 3.0L or 3.6L NA 6-cylinder boxer than a 2.4L turbo 4-cylinder boxer if I were going to be towing regularly, I can understand that fuel economy requirements have forced their hand here. Hopefully the beefed-up CVT they developed for this behemoth can hold up long-term. Are they planning on mating a transmission cooler to it?
Yes, it's tuned for 87 rather than 93 like the FA20DIT's, and the CVT is tuned to maintain around 2000-2500 RPM since this provides excellent torque. As you suggested, the market for the Ascent is generally people not looking to vroom vroom - that's what the 'Rex is for. However, they've also discontinued the Foz XT going forward, meaning you'll only find the FA20DIT in the 'Rex going forward. For now.
The CVT itself requires a specific and unique CVTF compared to the High-Torque CVT fluids found in the 3.6R (OB, Legacy) and the HTCVT in the 'Rex and XT's. From what I understand, it does have a transmission cooler - there's a difference in towing capacity between the Base and higher trims that I think comes into play because of this - but the Ascent forums are peering over a bunch of articles in which we thought there was a second transmission cooler which is appearing to be more of an oil-air separator of some kind, which is going to also help limit the issues related to DI and carbon buildup.
@Jag posted an interesting thread about a "carbon cleaning" type of Valvoline oil going forward, since it's his assertion (probably correct) that modern oils don't "reverse" the carbon deposits but are designed to "prevent" said deposits, so I'd be curious if there's something like this down the road (years and years).
I'm not looking to buy at the moment, as a better financial time would be sometime after next Spring (2019) because of other expenses I have going, including the Mrs.'s car payment, but, I'd be planning on getting an extended warranty regardless to protect myself from catastrophic damage. So, I'd get the $100 or $250 deductible program out to 100k miles and 10 years backed by Subaru itself.
It's also worth noting that Subaru is the type of car company that just might extend everyone's warranty out to 10/100 for powertrain components as needed because of unforeseen issues. I'm a perfect example of that - they just replaced my torque converter, at 85k miles and 7 years of ownership, for free because of an extended warranty. I have one of the first generation Lineatronic CVT's in the Outback. It was great customer-forward thinking that saved me from having to spend around $2000 on a car that's KBB'ed around $8000.
Peace of mind is worth something too. I may just run OEM Idemitsu oil in it for a while, even if I do the changes myself. From what I remember from looking at other UOA's, the OEM Idemitsu oil is generally good stuff, with good specs - but we don't know how it'll run in a FA24DIT yet since they haven't been launched yet.