Not sure DMGM would take Waters for him - he probably feels the same way many of us do about him - but if Waters would get it done this early there shouldn't be a second of hesitation IMO. With Smith/Jansen/Duvall coming off the books this winter (and the lack of OF help from within on the way), I'd think Benintendi's high-contact and low K-rate profile would be exactly the type of candidate AA should look for to fill LF for the next 3 years after 2022. If you could sign he and Dansby to reasonable 3 year deals the entire offense other than d'Arnaud would be controlled through 2025, leaving the only budget juggling to be done with the pitching staff - and that becomes a little easier with Morton coming off either this winter or next.
As for Russ' hesitation about going as far as Shuster for him, I get it. However, if the organization feels like he's another in the long line of AAAA arms that simply hasn't had the chance to be exposed yet I'd dangle him if that's what gets you a window to hammer out a 3 year deal with Benintendi instead of waiting until this winter. His current BABIP is high, sure, but there's enough data on him now to feel like you're getting a .330-ish wOBA/110-ish wRC+ guy at worst. That's a pretty significant upgrade over your other options PLUS he's another LH bat that definitely won't hurt you defensively as icing on the cake.