1. nice idea (but just make it simple weather and stacking with sch's storm or they'll complain)
even if they are not "avatar" per se it would make perfect sense to have something like that.(elementals symbolise weather on vanadiel after all)

2. not really needed. i guess a chance to take 0 dmg would be nice, but that's not a priority i'd say

3. could be interesting. not sure the exemples are good, but some nice buffs(or debuffs) added for new 2h bp could see some use.
Your suggestions could either be seen as overpowering or easy for SE to screw up.
not sure what could be screw up about giving new options. as for overpowered, would not be for dmg since that wouldn't be the purpose(still have the asralflow mp requirement too)

4. fairy sounds good(make her the white/blue pixie model please ^^; ), but i'd see her more like a "light spirit+1"(only cast cures/regen/buffs/raise) with improved AI(sea new automaton AI) and somewhat shortened recast time (and without the lame "cure/buff pj by sight" light spirit has)

also, why not give smn the "dual spirits" from heroes of abssea?(i guess spirits aren't what most smn want, so maybe making them a bit mode controlable that the classic spirits would help ?)

Err, we're getting Atomos and Cait Sith.
waiting them since what ? 2-3 years ? with no news at all for server test or anything ?
better start planning now if you want another before the servers shut down. >.>