I just want to make your statement clear:
You would risk to sent veteran brother with 160Fatigue and great mdef and rdef to the battle naked (or half naked with armour without Fatigue loss) with bare dagger to keep maximum Fatigue pool and expect to have immortal unit with this…
You can be stunned, sniped, poisoned, bleded, staggered, rooted, netted, asleep, charmed, fleeing and you would risk jewel of your company to go there without armour with an ability you cant use every round if you insist on combining it with recover perk. I can see a problem combining suggested Nimble perk with Indomitable perk, but it can be managed by simply making Indomitable not reducing damage done to the Fatigue pool.
I think it would be much better use if you take it as a one-round life insurance when things go dire with light armoured brother. You activate Nimble to survive the round in the front line by boosting his HP pool with your Fatigue, if you get hit you have to get out for atleast another 2 rounds to get Fresh again to risk the frontline. If you are not hit you just spent 4AP for nothing and nulified your Fatigue recovery.