i agree with your suggestion but i say simplify it. Each race keeps its original 25% bonus in addition to gaining 5% to all stats.
Also think race unique techs should stay.
And in the way of Asgard/Tauri accounts, upon ascending lose the neg benefit to their respective att/def.
So in essence here is how my suggestion would work:
Tauri 25 strike/-25 def
Tollan 30 att/5 def/5 cov,anti/5 prod
keep quickstrike tech in addition to AB
Asgard -25 att/25 def
Ancient 5 att/30def/5cov,anti/5prod
(kicking myself for this)keep hologram tech in addition to AB
Replicator 25% cov,anti (no neg stat as far as i know, correct me if im wrong)
Nano Ti Master 5att/5def/30cov,anti/5prod
keep resurrection tech in addition to AB
Goa'uld 25%production (again no neg stat i think, see repli above)
System Lord 5att/5def/5cov,anti/30prod
keep enemy conversion in addition to AB
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These are my suggestions for main, dont have much of an opinion on ascended server as i dont really play it.
Also leave ascended weapon prices and strength where they currently are? make bonuses from ascending be strictly unit bonuses?
opinions welcome
PS: if this get implemented (which i doubt

), give an automatic 25% boost to the related areas of those who are ascended and add a place to buy the race unique tech. what im tryin' to say is make it retro. this is has been my opinion of how it should be from the start, ascending costs enough in resources as it is, even if you do use the broker. and who is to say that when your new "advanced" race emerges, that they don't find some record of the technologies and techniques of the previous inhabitants of the planet??