Nic, I'm going through the same process right now and what I've learned is that to the extent that you give up the steeper seat tube angle, you loose aero position, mechanical efficiancy and cannot effectively use a tri set up. If you go to a more traditional road configuration and use clip-ons, you usually end up too stretched out in the upper body to be comfortable and you're not as aero.
One solution is to use a trad road bike with clip-ons that are positioned with the arm rests,more posterior, at the head tube area. These leave you less stretched out and more comfortable but don't solve the problem with the better aero position on a steep seat tube and mechanical efficiency.
My solution. I'm planning to buy a tri bike used or at a discount and save up for a nice traditional configuration road bike with a compact double for all the hill climbing training I do around here.
After everything that I've read, I've come to the conclusion that you lose a lot in both areas by trying to find a bike that conforms to both situations. As someone once told me... Use the right tool for the right job.
Living life like there's no tomorrow.
http://gorgebikefitter.com/
2007 Look Dura Ace
2010 Custom Tonic cross with discs, SRAM
2012 Moots YBB 2 x 10 Shimano XTR
2014 Soma B-Side SS