It's not a bad train of thought.Like that idea but.... Haters would say the UFC gave Hendricks to GSP because they are protecting him. As you point out Hendrick's "is a shell of a broken man", so they're giving him an easy fight.
Think Whittaker will happen then GSP will drop to WW to face Woodley. The Reaper trained at Tristar and GSP was the one who helped him with his wrestling defense, getting it as good as it is now. However Georges and Firaz also know Rob's weaknesses in wrestling and how to get him down. GSP would take Him down and sub him, that was one of Rob's weaknesses when he was at WW.
GSP will drop to WW and face Woodley. A fight made for GSP. Woodley, like many others would be too scared of the takedown which would hinder his striking. Rush, mixes it up with jabs, kicks, and takedowns and wins his WW title back then vacates the MW Belt.
If this happens and Georges wins both fights... GSP would be the only Two weight class Title Holder that defended BOTH belts. Conor would be pissed someone bettering his record. At which point Mac would call out GSP for a SuperFight.
GSP said when he first came back he wanted four more fights and had a plan. From what's been said from his coaches and himself this is my take on it.
If he pulls it off it would be something to see (apart from the Woodley fight, he will turn it into a boring shitfest)