My idea for a thermal detonator rework has been to introduce a new character or rework an existing one that has a unique that grants TM when TDs are dispelled. For example, introduce Jango, who has a unique that grants +25% TM to all BH whenever a TD is dispelled or a character does with an active TD.
You could also do some other things like that with uniques that don't require changing the core mechanics of detonators. For example, a unique that reapplies them (like Vaders leadership). I'd prefer routes like these over redoing the entire game mechanic.