Ignoring the myriad of things you don't even know a GM does and sticking strictly to player-personnel issues, what--exactly--would you do, and in what order? Try to keep reality in mind: no Velez-for-Pujols trades need apply.
(My own thoughts below the jump.)
It's bitter, but sunk costs are, well, sunk. The team needs to recognize that, get over it, and move forward. I have numbered these for ease of later discussion, but they are pretty much all of equal priority, which is urgent.
1. Excise Molina from the roster, literally a.s.a.p. There are teams who think themselves contenders who have had catchers go down, and that's a starting point. In trade offers, go for what might be had, but be willing to accept a 73-year-old ball dude (meaning a face-saving organizational player) and no cash in return. If nothing whatsoever materializes at once, bite the bullet and DFA him. A team that would take both him and his remaining contract, even with effectively zero back, would be a gift.
2. Tell DeRosa to have the surgery now. A healthy DeRosa in 2011 is a needed asset, because this organization has no worthwhile position-player help in the near pipeline (if any anywhere) and few trading chips of any value.
3a. Wellemeyer is just not a pitcher with a role on a team that wants to win something. His occasional teases are just that: he has no history whatever to suggest that he is anything other than league-average or worse. Flush him out in much the same way as Molina: whatever you can get, if anything, is just a bonus.
3b. Maybe Bumgarner still has things to learn. Let him learn them from Dave Righetti. Starting now.
4. Rowand, at his best, is a below-average hitter and only so-so fielder. He, too, has to be gone, though the rush is less imperative; in time, his BA will probably go up (low BABIP right now), so hold on, play him maybe 2/3 time, mostly in LF, wait for both his value to rise a bit and for someone else's needs to be more pressing, than dump him for whatever you can get back. Screw the money, it's long since blown out the window.
5. Get a good, solid, young--just ready for the bigs--outfielder. Do this by trading a real-value correspondingly young pitcher; the starting staff is set for a while, so a Wheeler or a Maday can be let go if corresponding value is gotten back. A CF type is preferred, but a corner is acceptable if he is at least defensively average (and, of course, is a great bat).
6. Fire Bochy. And Flannery. Wotus interim, till a suitable candidate aware of the arrival of the 21st century can be identified. (For all I know, that could be Wotus, or Decker--but please, no knee-jerk "from within" hirings just for the sake of it). A sane manager will give the position players playing time in something like the rotation I laid out elsewhere. Oh, screw it, I'll repeat it here:
Player : Day # 1 2 3 4 5 6 Torres CF x CF CF RF CF = 5/6 Schierholtz RF RF RF RF x RF = 5/6 Rowand LF CF x LF CF x = 4/6 Bowker x LF LF x LF LF = 4/6 Uribe 3B 2B SS x 2B SS = 5/6 Renteria SS SS x SS SS x = 4/6 FSanchez 2B x 2B 2B x 2B = 4/6 Sandoval x 3B 3B 3B 3B 3B = 5/6 Huff 1B 1B 1B 1B 1B x = 5/6 Posey C C x C C 1B = 5/6 Whiteside x x C x x C = 2/6
(But we hope Rowand is replaced by a traded-for-pitcher new OF.)
7. Get Casilla and Bautista back to Fresno before the otherwise-inevitable blowups can occur. These are guys who can look good for a while because they can throw hard, but each has a well-established major-league history of major failure. Find out, right now, whether any of Sosa, Hacker, or Pucetas is useful or not; none is likely to be worse than Casilla/Bautista.
That's about all that is immediate. For all the grousings about the veterans, there's nothing better in the pipeline save pipe dreams. Maybe Neal or Crawford will suddenly perk up, but it's a hard truth that AA is where they separate the contenders from the pretenders.
The organization needs to be rebuilt from the ground up. We try to skate by with what we've got (after the moves above) and hope the scotch tape holds for a couple of years.