All right, as long as we're blue skying and providing free consulting advice to the yet to be consummated deal, here are my ideas:
1) Assume international hubs at ORD, IAH, EWR, SFO.
2) Assume international gateways at LAX and IAD.
3) Assume regional hubs at DEN and CLE
4) Provide select international service from MIA, SEA, JFK
Identify key airports with capacity issues and reduce regional service, while increasing seats to hubs. ORD is the biggest benefactor here. The problem with ORD for UA is that it is trying to be all things to all people. The delays, IMHO, are largely due to over expansion of regional service from AA and UA. And what I am talking about is getting rid of the very small destination traffic that can only support RJs. If the destination can't support mainline from ORD (and other hubs) several times a day, they get RJs from elsewhere. But what you do is increase seats to CLE and let the RJs scatter to the four winds from CLE and DEN.
Utilize airports with capacity to burn as regional hubs. Since CO will likely take it in the shorts from the city of Cleveland if they abandon that investment, make CLE the East's RJ hub. Do the same for the West with DEN. IAH can probably handle a mix better than ORD. IAD can probably also handle the mix. If additional capacity is needed, I'm willing to bet good deals could be worked out with PIT, STL or MCI. (And possibly DTW, CVG, MEM and SLC in the near future.)
A particular challenge in this world will be wrangling the UX carriers and ExpressJet and convincing them that this is a good idea.
The bugaboo in this strategy is trying to streamline the manner in which you get folks from a relatively minor market to an international destination without making them connect twice. Right now, if a guy from Oshkosh Trucks needs to go to Europe to sell equipment, he can fly direct to ORD and get pretty much anywhere. Under the new scenario, he likely flies to CLE and connects to EWR and then onward. (Or, more likely, flies a NW/DL RJ to MSP and then KLM to Europe.)
The guy in RDU that needs to get to OMA is probably flying RDU-CLE-OMA, which is probably better than going through ORD. If the guy in RDU needs to go to PEK, he probably is getting a RDU-CLE-ORD-PEK routing, versus RDU-ORD-PEK today.
ORD becomes the Northern hemisphere International hub and a mainline domestic hub.
IAH becomes the Southern hemisphere's hub, with a focus on Latin America. It is also a mainline domestic hub, with some RJ traffic.
SFO is a Pacific hub, with LAX picking up some capacity and SEA available for cargo focus.
EWR is the European hub, with IAD complementing service. (One thing that no one has noted is that CO flies to India, ex EWR.)
MIA and JFK are used for seasonal Caribbean service.
Business1 (such as that exists anymore) continues ex ORD and now IAH, with IAD. The main idea is to ensure hourly mainline service to LGA, BOS, DCA, plus frequent service to PHL, ATL, DFW, and MSP to provide alternatives to AA, US, and NW/DL.
There is also a need for BOS-LGA-DCA direct services. Arguably, that could be handled by an expansion of CO's relationship with Amtrak for Northeast Corridor codesharing.
I'm not sure what you do with Continental Micronesia, but if it works, keep it.
The routing is seriously complicated, but a bigger airline also allows for more flexibility and options. If you have IAH and ORD as mainline hubs, you are in a much better place to shift traffic when the weather goes sour. If you move your RJ ops to places where capacity isn't as much of an issue, you again provide more options when the weather goes sour.
Operationally, the 733's are off to the desert pretty quick. If you need more of their capacity, you infill with RJs (Emb 170 / 190 class in particular).
Keep CO management, *A, upgrade the RCCs to CO standard, and retain M+ and perks.
Ted is toast. To compete with AA and NW/DL, you will need an F product to "leisure" markets. AA, NW/DL and UA/CO will need to differentiate from the LCCs and mainline food, E+, F, and upgrades are the way to go. The A319 / 320 aircraft are problematical, if only because CO is all Boeing. The UA 737 and 757 fleet is also problematical simply because the vast majority of them are at least 15 years old (is it worthwhile to invest in upgrading old airframes or simply trying to get newer ones?). CO has newer 757s, but has the same issues with the 733 and 735s. The good news is that CO has been buying the 737 NGs for a while (and has some on order).
Still, neither airline has a lot of money out there for new aircraft. However, if the economy continues to soften, will some newer aircraft be made available on the used market if some airlines go bust?