It depends on how "rich" the rest of the world and the campaigns are. If you are flying over the channel and there's only water it will get somewhat repetitive after some time, unless you really do like just cruising around. If there are friendly ships signalling you, enemy ships shooting at you, seaplanes patrolling and rescuing downed pilots, chatter on the radio, civilian ships that you could inspect, targets of opporunity, etc...then, if you couple this with the advanced engine management in SoW you'll be having your hands full.
Another thing i noted is that when i accelerate time in single player i can't "settle in" the way i do when flying manually and nor can the airplane. When i fly the entire sortie (as in multiplayer), it seems as if the aircraft behaves better, since i can gradually adjust power settings, trim, etc as i climb to the target area. So, if time permits i like flying the sortie myself and settling into the situation. With advanced engine and systems management to keep my hands full, i don't think it will be boring. It will just be a case of "how much time do i have?"
However, having a 1:1 map and saying "it's not a problem in single player thanks to time compression" is like saying "it's not a problem because i can accelerate time 32x, so i can travel the 1:1 map like it was a 1:32 size map"
What i'm trying to say is, the detail of the 1:1 map would be lost if we were always flying with time compression, that map probably will deserve to be flown in real time. Of course, when in a hurry people will compress time in the sim and just having the wider feel of the big map is enough of an excuse to use it.
As for multiplayer, it would depend on each server's character...what kind of people it attracts, their preferred difficulty settings, etc, plus they could mix map sizes for more variety. I think that having a rotation with 2 small missions on the scaled down maps and one long mission on the 1:1 map would satisfy everyone. The small maps would be good for quicker action and multiple sorties, the big map would be like a more "strategic" affair, with more places to "hide" your flights, more distance to cover so that even if you know your friendly targets are being attacked you might not make it there in time to save them, etc.
Having real life distances would also shift the tactical balance towards more realistic and varied scenarios, as people will be unable to gain free performance by flying around with 25% fuel. You might meet someone who's low on fuel, he might choose to run away or use his lower weight to quickly shoot you down and escape afterwards, etc
Of course, 1:2 or 1:4 versions would be welcome for online events or smaller sorties. I think i would fly equally often in all of these maps, downscaled or not, depending on my mood and available time.