1. Yes, it's a bit of an exploit that will never be fixed. Consider it a feature. It is the only instance in CoH2 where a player has any interaction with pop cap. It's not like it's tied to territory or anything, and there's no global upgrades or anything (except I guess Bolster Squads) that impacts it in any way. And matches where players reach 100 pop cap are more exceptions than the norm, at least for USF. Only times I can recall using it to my advantage is in 4v4s where I've got like multiple Calliopes.
2. It is a benefit. And to be honest, a particularly cool one. It's a unique little component of the faction that is worth preserving. I'd say it's way better than say, merge, but it's similarly rather fun without being game breaking.
3. I'd agree that looking at repairs, USF has an advantage. But it's rather slim and acceptable for the faction. But it's apart of the greater pattern with USF and RE's roles being partially filled by every other unit. Repair critical is nice, but in my experiences if you're able to get to a position to use it, you probably don't need to use it. Unless you're recrewing an RNG abandon, which USF is totally better at if they got a vehicle crew handy.
4. I'd rather there be more instances of this in CoH2 than fewer. I'd love to be able to abandon a team weapon for an ally and such. And (for instance) while the British weapon drop halftrack has all sorts of issues, I only find this strategy to be worthwhile in 3v3+ where units and factions pale in comparison to teamwork. And that's an environment where the game is fundamentally unbalanced for that exact reason.
To conclude disembark is great ability available to USF crews with a number of benefits.
Well, duh. It's a core feature of the entire faction.
To be honest, I wish this were a more prominent feature of the game. It would have been quite interesting to be able to decrew all team weapons and vehicles. The value of preserving the original crew and their vet would've been worth exploring. I could never could get it to work properly in tuning packs.