@Kamer Hello! I have a suggestion. It would be cool if walls could get various cracks on different persentage of health and have no cracks after repaired.

@Birget Can't change the look before repair, but I'll think about it being replaced after repairing it.

I suggest to remove repair option from doors. To do so check if it's door or a doorframe(via moddata) just change media\lua\client\RepairWall.lua (line 38) to
local moddata = k:getModData()
if instanceof(k, "IsoThumpable") and saveK[k] == nil and not (instanceof(k, "IsoDoor") or k:isDoor()) and moddata.wallType ~= "doorframe" then