Further more...
On Ausmus, while I believe they will bring him back (for whatever that's worth), he's going to be 37. It's unlikely he'll be able to catch 80% of the games the way he did down the stretch this year. For that reason, I think it would be a smart move to go after Ramon Hernandez, assuming he has not employed Boras as his agent. Benjie Molina would also be a nice addition but I haven't seen much of him. The only thing I know is Molina is a couple years older than Hernandez. From what I saw of Hernandez, he's quiet behind the plate, frames well, and doesn't mind getting in front of pitches in the dirt (anyone else have an opinion on him, please share as I'm purely amatuer in my observations). Seems like a good replacement for Ausmus, IMO. That also assumes that there aren't a dozen other teams after either player. But the net of it is that Hernandez is a good catcher who can also hit fairly well.
It's a tough call on how the Astros upgrade the offense given the defensive assignments. I'm not jumping on the dump Ausmus bandwagon but at this stage, I think he's a better second/personal catcher for guys like Pettitte and Oswalt or Pettitte and Clemens, if Clemens returns. If you get a guy like Hernandez, who will command a hefty salary, it alleviates some of the offensive needs while not depleting a critical defensive position.
The big obstacles are whether Clemens returns and waiting out Bagwell's situation. No one is going to make either retire. It's arguable whether they will contribute as much as they have in the past but they will contribute. Clemens for <30 starts is still better than Wandy or Zeke for > 30 starts.
Bagwell's in a different situation with his shoulder. I'm not the only one who questions whether he'll ever effectively play the field again. He may opt for a PH role. I'd be shocked but it's feasible. If he does retire, I'd also be surprised if McLane doesn't buy him out instead of expecting him to waive $18mil in the final year of his contract. That's insanity. Hell, at this point, McLane owes so much money to Bagwell, he may as well offer him a share in the club as his buyout.
Anyway, getting back to the point. Clemens is likely to be the more productive player, of the two, next year if he chooses to return. If he retires, I doubt Houston goes after a FA pitcher. Given their history of staying with home grown pitching when an obvious choice isn't available, it's going to be Oswalt, Pettitte, Backe, Wandy, and Zeke. I don't see that as a bad rotation, just not as good as this past seasons.
The key to the pitching staff, IMO, is either keeping Springer or getting another quality arm in the bullpen. A lefty wouldn't hurt but any RP who is effective against lefties is a plus.
On Dunn, it's an incredibly huge assumption that he's going to be available via trade. If he is available in a trade, I can't imagine Cincy not wanting the sun and the moon for him.
While I'm on the topic of pipe-dream trades, the Astros wouldn't be wasting time looking at Aubrey Huff. Again, the D'Rays aren't going to part with him cheaply.