Have you looked at partners' desk configurations? My current desk is actual a true partners' desk where there is a drawer on either side (although we don't use it that way). It's an interesting concept, especially if you don't have 2 people who are really needing lots of desk space at the same time.

We used two desks back to back in our office with a similar layout as yours. One of us has our back to the window and the other one to the wall opposite. It works nicely. We used desks from Crate and Barrel and they look fine that way.

Or buy a rectangular dining table. Place narrow end to the nice window and run wall cabinets on either side of it. Get a couple roll around drawer units that can be parked under table next to wall or under the wall cabinets when not in use. Should be comfortable for people at the table/desk and leave you plenty of room and air space for the cycle so you are comfortable working out in there.

to enthuziast- where did you get that great shelving unit?