This spell could've been buffed or reworked, it feels like a wasted opportunity.

It's a 9th level spell that lets you buff or escape for maybe 2-5 turns. Incredibly disappointing that it wasn't reworked or buffed in any way

Running Time Stop without the second paragraph is really fun. 

I think you can use the last turn to cast a big spell like mass suggestions or earthquake or whatever. And I think you can also use your second to last turn to ready an action to cast a spell as a reaction?

So say you got 4 turns. First two turns do stuff like buff yourself or summon monsters, then 2nd to last turn, ready an action to cast a spell with the trigger being, an enemy takes it's turn, and then with your last turn cast an offensive spell, ending the time stop right when it would haven ended anyway. then fire off the prepared spell the next time an enemy acts.

I might be off on all that though.

I don't think the prepared spell thing is intended. Since you're the only one taking turns, it's essentially a round passing which prevents your reaction prepared spell from firing off. Best you can do I'd say is make a wall of force (or some other dangerous barrier) around an enemy and cast buffs, but buffs and wall spells both tend to be concentration so you can probably only cast one before making your big attack. Maybe the new sorcerer could get some value out of it by activating their powered up state during the turns. Still, even it let you take 4 actions where you can effect everyone normally and they can't counter it, it still wouldn't be anywhere close to the strongest 9th level spell.