While riding I came to the conclusion that I won't buy another bike for the trainer. I mean, that just doesn't make sense. Spending a boatload of money won't help me finish the ironman! I just need to train more, especially on the bike.
After I get my Trek back, with the powercranks on it, I can use it for pedaling drills. For the trainer, I'll use my Cervelo. As for riding outside, I can also use the Cervelo. If it is raining, I am 95% likely to ride by myself, in which case I don't need fenders (and thus can ride the Cervelo), or can be as slow as I want (and thus ride the Trek with powercranks).
Basically, I can take the 10 minutes or so to put the Cervelo on and off the trainer, to save hundreds on another bike.
What I am willing to do is investigate finding a different aerobar system for the Cervelo. I think the Cinelli's are very agressive, and I just can't get comfy enough as my torso just isn't that long. This issue came up during my bike fit with Erik Moen - he said he would shorten the stem except he couldn't on my setup, and the seat is as far forward as he is comfortable putting it. I don't want to be overbalanced and fly over the handlebars if I have to brake hard!
So, after I'm back from Christmas I plan to take my bike into Sammamish Valley Cycles and describe what I want. Even though I didn't buy my bike there, I am sure they can help me change around the handlebars/aerobars/stem.