So your optimism depends on him ranking around the 10th percentile of all (qualified) batters in BAPIP? Good luck with that.
I wouldn't rule it out entirely, no.
And you're talking about a .750-.770 OPS and I'm talking about an .800 OPS. That's about 7-8 hits scattered over the course of a season, or about one extra hit every 20 games.
Is that truly unreasonable?
The fact is that neither you nor I have any idea where Grossman will land when it comes to BABIP because he doesn't have the track record one way or the other.