I work at JSC. It has been a long weekend for us, and many long weeks to come.
First, my own personal opinion*, I think it's time the Shuttle was updated. Not piecemeal, but from the ground up.
I think that the requirements should be pretty simple: We want something roughly Shuttle-size and shaped, to minimize changes to the stack.
We want it tougher, stronger, and simpler. No fragile tiles, modern engines (which are far simpler than the Shuttle's mains).
Redesigned frame, on the same scale as the Shuttle, but hopefully with a better reentry profile. Hopefully lighter, but with a hull and wings than can withstand reentry (and space) without being as fragile and easily damaged as tiles.
Improved avionics, eletronics, computer and sensor systems. Better "automatic" diagnostics, better data on ship's systems, and far more efficiency. With fewer parts.
Ditto engines. Ditto fuel cells. Ditto everything.
It'd be swifter, and faster, to start with what we know, and simply do it better, than to build one entirely from scratch.
* Not affiliated with NASA in any way, and I'm a software engineer, not an aerospace engineer. I do know that if I'd actually gotten around to applying for MER access (it was low priority), that I wouldn't be here, but in the MER trying to recover data. Which sucks. I could be helping, but because I didn't fill out the MER form because it was for future work, not what I'm doing now, I can't.