Re 4: Not 100% what you mean. It's not exactly like good players that pull of perfect moves never have to hard retreat, right? There is surely a tradeoff. Like, yes, of course, a player that gets one of his units suppressed should get punished. How much, though? Would a 2 minute retreat be sufficient? 5 Minute? 10 Minute? At what point does it get boring to wait? And yes, ordering your units around in whatever way is typically more fun than waiting for them to retreat/get healed/repaired and so on.
I'm saying that FRPs are there to just circumvent the nature of big maps which on tops degrades the game into more spam/blob fest till one side has a big enough of momentum to overwhelm the enemy blob/army.
Retreat times to HQ are equal for everyone. I think the initial design for FRP was for factions with limited
stage powerlevels, tools or utilities to recover terrain after losing initiative. By taking a look at their vanilla release, you can see how much they have gain since then.
The one which makes little sense IMO is the UK one, unless the main design for it was to bring "balance" to 3v3+ and there you NEED a FRP.
Note that this is my critic to the current LIVE FRP model. I wouldn't mind a more proactive decision making around them.
For ex: wild idea for USF (OKW having a static med HQ makes it less flexible). Major setups a radio/beacon/whatever structure point as a FRP. Cost mp/extremely fragile. Now, the major get's an ability with a certain low cooldown (you can't mass retreat blobs) which forces single units to retreat to that point. Can't be cast on pinned/suppressed units nor while the major is under those effects as well. Range is big (50-60) enough for the unit to be on the backline without entering combat.