I dont know why i didnt brought up this earlier but here goes. (probably because its difficult to implement)
Current Behavior: Whatever Timestop does doesnt stop spells from running out. So using Timestop is hurtful with a buffed party, even if they are "frozen", their buffs miraculously arent and will run out.
Expected Behavior: Timestop stops spells from running out on affected targets because they are frozen in time. Unless dispelled ofc.