Didn't she already appear in that one Flash/Wonder Woman arc teaming up with Zoom before The "Rogue War" arc ?

Yes and i would not mind if Minerva develops a connection like that again.

Yes.

I wouldn't mind her showing up to fight him in a story or two, but I dont think she should be shared between Diana and Flash on a permanent basis.

I do think it would be good to have FLASH team with Wonder Woman when Cheetah taps into the magic speed force, but honestly I don´t like other people stealing WW´s classic villains.

I do think Cheetah should be in Suicide Squad.

I don't think any big-name villain should be on the SS save as an example of why the team usually consists of mid-tiers at the very best. SS is sort of a dumpster for disposable supervillains that can't cut it on their own any more. Like take the last time they tried adding some muscle to the team, that candidate was Zod, and he lasted about 3 issues before he pulled the bomb out of his head and wrecked the place.

Cheetah I feel should be something of the same. And it should fit with Waller's MO, she only puts people on the Squad she can actually control through intimidation. With Cheetah Waller will likely know that putting her on the team would come with a timer going down to when Barbara looses her marbles and kills everyone in the room before anyone has had a chance at stopping her. Though I have to admit that imagining her and Harley being stuck in a room together could be amusing.

She hardly gets any appearances. It's strange to be completely honest.