Guard Stance I believe was supposed to double your regeneration and force regeneration and prevent the player from using critical strike, flurry or power attack while it was active (Meaning it would possibly be a feat you needed to activate similar to Hanhar's Wookie rage feat in K2). So since regeneration doesn't work in vanilla K1 and I doubt activating a feat and disabling other feats can be a thing I doubt Guard Stance can actually work. As for Grenade and Simple Weapons feats, I have already made Simple Weapons a feat- http://deadlystream.com/forum/files/file/1062-simple-weapons-feat-restoration/ the mod could use some polishing up though. As for Grenades I do not believe I could get them to work as you don't need a proficiency to throw a Grenade and I doubt Grenade Focus and Specialization actually give a +1 or +2 damage though if it did Grenades all ready to tons of damage so I doubt a +1 or +2 is going to make a difference. Also, there is a Skill Focus feat that gives +2 to a skill for example Skill Focus Persuade gives +2 to Persuade but again I don't think it works.
As for Guard Stance, I wouldn't mind someone scripting new properties for the feat all together so it still seems like a "Guard" type feat but doesn't have the horrible no attacks part (Perhaps it should give extra dexterity or a defense bonus) and I also wouldn't mind someone scripting Skill Focus to work like they should or maybe making it a feat that makes a Skill a class feat like the TSL class skill feats.