It's hard to say whether or not the Orioles will take a rule 5 pick. So many unknowns and a lack of recent data and observation. They pick 5th, and they would have to really like the talent to take one, I think. They have the room on the roster if they want one. It may be more likely they pick up a waiver claim, maybe even find a bargain free agent on a one year deal.
If you find an upgrade to Ruiz that makes sense, great. Do it. I see him staying for now because, as Tony said, a quality 3B is hard to come by. He's a LH bat on a team that is RH dominant, and his defense is better than what 2020 bared. Also, Valaika might get consideration for more time at 3B. I am curious what he would produce with regular playing time there, instead of being at a different position each day. Fangraphs has his 2020 season valued at $1.9 million, so his arbitration estimate of $1.1 is probably going to be seen as reasonable. https://www.fangraphs.com/players/pat-valaika/14885/stats#standard
Doesn't make a ton of sense to me, assuming Mancini is actually ready to go.
Mancini/Santander/Mountcastle/Stewart would seemingly be penciled in for 1B/LF/RF/DH with Diaz on deck by mid-season.
Puig may well be an improvement on Stewart or even Santander/Mancini, but this is hardly the season to be focusing on marginal win improvements at the cost of short-term free agent signings.
Maybe a L/R platoon situation with Stewart plus filling in for Mancini once or twice a week and Santander and Mountcastle whenever they need a day off. I assume Mancini won't be playing 155 games.
Puig is only 30 (in two weeks), but I'm not sure how he could get a multi-year deal now considering he couldn't get one last off-season.
Apparently the Orioles are still kicking the tires on Puig as a free agent, according to several articles.
I don't see it myself. But it's being reported.