Hello Odisseo,
1) No. I do not think that there should be any increased rewards for extending a streak of kills. Perk-farmers and score potatos are bad enough with the tools that they have now.
WHat's a perk farmer?
As far it was in IRL the task of the air fight was above all to survive and not to get kills, from those who was surviving there was some who managed to land kills (Aces).
I personally don't need the streack multiplicator, I will anyway and allways work on my streack instead of the number of kills, but maybe to implement such setup more peaple would fly smart and we wouldn't see (or maybe we would see less) scores like 800 sorties 750 death and 1000 kills

Anyway all good idea have a back side, and where many enjoy the benefits of new ideas...some they misuse it..but who cares, if somone want to collect million of perks...if it mak him happy..who cares, what's important is that everyone must have fun, and I don't see how streack moltiplicator would ruin the fun of someone.
Anyone's free to fly what he wish, how an where he want, I just wrote an idea

2) Yes. Great idea!
I just ordered a book from the national army library, Switzerland has a long artillery tradition (i'm artillery officier), and there are most example we could use from 1928 till '60 with all detailed informations.
p.s. I would love to see/lead a coordinated air/ground attack with some artilley battery, close tank cover, and great ground incursions with artillery cover and finally we would use the jeep as scout/fire director giving fire corrections...wow!
3) Yes. Great idea!
4) Yes. An idea that I have seen put forth before, but definitely a good one for the game.
Think if we would have shenarios with sea war with actual CV convoy but with those sea beauty together!
Tirpitz

Bismark

Yamato

King George V

Greets!