Ok, after doing some math, i've reach the conclusion that the best build for grima is warding breath + wary fighter + glimmer + CD seal. With this build, he is able to survive any engagement except from falchion users, full buffed red/green blades, armorslayer units and high atk brave sword users, and kill almost all units in the counter attack.
The question is, should I kill my only V!like (the free one) to give him warding breath? (My grima is +atk -spd) I really dont wanna loose my only V!like dispite i didn't botherer to lvl him up, but grim with his default kit seems a bit lackluster to me as he dies more often than you expect from him. Also, that build is very colosseum oriented, and i feel that his base set + aether is better for chain challenges and tempests.
Im surprised no one gave a response to your post in almost 4 hours, hmmm depends if you have better sword units than V!Ike, warding breath can work with grima but id wait and see what units you can get "if" your pulling in the legendary banner. If not id go ahead with warding to grima, least he will do better against dragons and mages
I think you can give the Warding Breath away, but to what use?
He has an in-built ability, taking down his cooldown on B
You also don't need the Wary Fighter, if you're putting him in an armour or dragon team... why are people afraid of getting doubled, if the enemy deals no damage any way?
You can simply decide to let someone else take care of threats to Grima and position him somewhere else, where he can still do a double counterattack, instead of a single one.
By the way, if you're not running Grima in an armour or dragon team, then i advise to not use him at all, since he is an enemy-phase unit and relies on the buffs etc.
My personal opinion on builds around Grima are:
Close Def 3
Vengeful Fighter 3
C (optional depending on team)
Aether/Glimmer (haven't tried Noontime, but has potential as well, healing back up at each counter attack)
Reposition/Swap/Pivot
SS Distant Def 3
Pokemon GO
Fire Emblem Heroes
Fate Grand Order
Dragonball Legends
Dragalia Lost
IV Calc
Heroes