I don't think it's a 1-for-1 with Flaherty even if you've listed a headliner prospect. IMO, I think at a bare minimum it's 2-1 or 3-1.
As for Rushing, I think scouting reports are he's not a great catcher, so short-side or backup catcher, plus a lot of 1B risk... but IMO, still a useful guy. But he's taking short games at catcher (20-30 per year) with a dominant catcher (let's call him Dingler) and then you're plugging him in at sometimes 1B, DH, PH'er... So he's limited IMO, but still very useful in spots, especially with the bat. IOW: It's the bat that's being traded for, not him as a starting catcher.
That says: Who else is included? Per my 3-1 trade... I would jump at a Rushing + Freeland + Jackson Ferris package (RatkoVarda proposal...).