Have you ever been to the Palm Springs airport?? I have flown in there multiple times. Mostly on EMB-120 Brasilias! There is a reason why there are many 30 seat turbo props and 50 seat RJ's on these routes. Palm Springs does not have that much demand. It is actually somewhat of a trick for flying standby on United. To get to vegas, fly SFO,LAX,DEN TO PSP, and then connect PSP-LAS. Worked for me last memorial day, when they were using denied boardings on my direct flight.

Pretty much you got United from SFO,LAX,DEN,LAS on 30 and 50 seat commuters. US Air from PHX, and like one flight from LAS. American from LAX, and Alaska from SFO on MD-80'S, and Delta from SLC on RJ's. And these flights are not full. Palm Springs is a relatively small town. I went there on vacation at least once a year for 5 or 6 years, and I love the town, but it is pretty darn small.


Now that I have shot down your PSP idea (it's for the better), I have two recommendations for your hubs.
San Diego
Sacramento

San Diego (SAN) is the second largest city in California, (one of the largest on the west coast), an amazing vacation town, and perfect for a low cost carrier. No carriers are currently hubbed there.

Sacramento is the capital of California, and the suburbs are growing rapidly. This city can definately support an airline hub, and no airlines are currently hubbed there. The nice thing about Sacramento (SMF) is you are centrally located on the west coast. For instance, you can have a plane originate in SEA, fly to SMF, and continue on to SAN. Passengers can stay on the same plane, and the flight time is only slightly longer than a nonstop. However, the flight time will be significantly less than going, say (SEA-SLC, (change planes) SLC-SAN).

Both of these airports are not terribly busy and weather delays do not seem to be much of a problem (occassional valley fog for SMF).
LAS and PHX are TERRIBLE ideas. First, you already have US Air hubbed there. Next, you are competing in Southwest's strong holds. Yes, these airports are busy, but literally every airline flies from everywhere to Vegas. And these fares are already pretty low. Plus, with all the MOA's around Vegas, it is not unusual to fly a long detour at low altitudes (FL 270 or so) to get to your destination. Not a lot of direct routing is allowed into Vegas. Also, the last few times I have flown there we have had busy related delays. I would not recommend these two airports.