Agree completely with your first sentence, and I like Ellenson well enough, but is he redundant with Olynyk? I guess if we assume Sully's gone, having two offensively versatile, stretch big men who aren't really rim protectors is good, but there are a handful of guys that I think have considerable defensive upside- Deyonta Davis is another late lottery projection that I'd prefer over Ellenson. And Steven Zimmerman, Damian Jones, Diamond Stone, and AJ Hammonds all should be available later. Certainly all have significant warts, particularly on offense.
As far as win-now guys, Hield and Dunn would be the target for 3-6, with Valentine, Caris Levert, Taurean Prince and Brice Johnson as the other guys potentially capable of contributing something to a winning team.
Petr Cornelie is my annual youtube-mixtape international late round target. Bender-lite, he's a coordinated 7-footer who can shoot, but doesn't look ready to battle with guys down low in the NBA.