I've been looking for a pair of convertible pants that aren't baggy. I currently have a pair of Columbia convertibles that are better than the REI brand pair that they replaced, but are still pretty baggy (and lack zippers at the ankle). I had come across North Face's Straight Paramount 3.0 convertible that were decently slim thoughout the leg, but the fit otherwise was really odd and unfortunately didn't work at all.
Any other convertibles that are known to be slim fit? For reference Prana's Stretch Zion Straight fit me very well (but their convertible fits like their non-'straight' Zion pant; i.e. baggy).
Hopefully you found pants by now! If you're still looking for the perfect pair (seems never ending!), have you tried Kuhl Renegades? My partner started with a pair and now wants to live in Kuhl pants all the time. Zip offs are great for riding his bike to work when it's hot (is it ok to wear convertible pants to work?).