In my opinion, keeping Simons is only viable if he signs a team-friendly deal longer term.
If they have a sense that he would be willing to re-sign to something much smaller than his current $27 million per year, then maybe it's worth considering. But if that's not possible, they might be better served using him as a trade piece.
The other point of your post -- namely drafting a big regardless of what else is available -- is something I'm fine with. More than likely they'll be picking around 20-25 anyway. History tells us it's a crapshoot at that point.