Um, what? I fail to see how it is MASSIVE. If they don't re-sign him during this season, when they'll know very little about him due to very little time to learn the system, then I'd say they have a very SMALL advantage, IF ANY, in signing him due to... familiarity? They'll basically have 2 extra months to woo him, but if he gets beaten up behind that OL and decides he doesn't like losing, he may actually have a bad taste in his mouth and would prefer to sign elsewhere as an unrestricted FA. They will either have to compete with all the other QB needy teams or they'll have to way overpay for an unknown by using the franchise tag... and then do it all over again next year. Overall, I'd say this advantage is borderline negligible and could easily turn into a negative.
Again, this is based on them having some sort of re-signing advantage which only exists in your head. There are some good QB candidates in this draft. Do you really give up on them to trade back and sign JG long term based on 6-7 games where he probably only learned half the playbook and had zero chemistry with his receivers? He could easily look decent in these games, due to defenses not really game planning against him, and then take a step backwards next year while some other team drafts a franchise QB with that early 1st. Or he could look bad this year and then take a step forward next year when he gets to properly prepare for the season. This trade is such a waste of time and draft capital it seems like a bad joke.
They're in a dead heat for 1.01... they could screw that up if Jimmy is an average QB. So they'll have paid an early 2nd to lose the 1.01. There are so many bad scenarios here that it is hard to pick the worst one. And again, I don't really see any awesome best case scenario - if he looks really good SF just drove up the price for him. If he looks really bad, which could be for any number of reasons, they have a tough choice to make and just cost themselves the 2.01. Lose-lose.
Hahahaha. What? NFL GMs had half a season of watching Brock, a full season of watching Matt Cassell, half a season or more of Glennon... those were all poor signings with more tape than SF will get in these 6-7 games. Sure, they'll get hands on experience with him, but they get hands on experience with free agents, too. This is an inexact science and throwing him into the fire late in the season isn't going to lead to a fool-proof evaluation. I mean, Adam Gase had a full freaking season with Jay Cutler in Chicago, paid him $10M to come to Miami, and that was a disaster. Evaluating JG for a few games without an offseason to learn the offense is not going to be as useful as you seem to think.