So I can see these Rotoms hitting a certain weakness once tools are in the discard pile (I'll go with the Gourgeist option to discard tools for example's sake).
-The Fire Rotom can do some damage against Solgaleo / Metagross in a Gourgeist deck where otherwise you would have a hard time getting a knockout on them. Sure, you can't get a 1-hit knockout on them, but 220 damage with band leaving them at 30 seems fine. Speaking of which....
Oven Rotom: I suppose it hits for 160 against Golisopod...
Just slap a choice band and you'll get that knockout
-I expect the lightning Rotom to hit Lightning Weaknesses, things like Ho-oh-GX, Gyarados-GX, etc. (Not a lot of lightning-weak pokemon but something to note)
-Fan Rotom is Promo Koko with the conditions set. Though, Promo Koko can attack very early but this really can't, that's probably the key difference. You'd have to imagine that by the time you discard 9 tools you're already in the late-game, and by that point you're probably OHKOing things with something else.
You never know, we might get a card that will support this kind of effect. I wouldn't exactly say Battle Compressor's coming back, since that's a Team Flare Gear and Team Flare cards are probably never going to see new cards, imo. These Rotoms are alright.