Originally Posted by ColinL

It's worth a shot, but by the looks of the rear shift housing, there could be problems. the first pic makes the rear housing look ok, but then in the last shot it does look like the loop before the rear derailleur is a bit short. The bends up front aren't ideal and might be improved by pushing some housing through the frame, shortening the section up front and increasing the size of the rear loop.

One thing I would be curious about on your internal cable routing is if it's an open lower tube or if there are internal connectors between the left inlet and rear exit, and right inlet and front exit. If it's an open lower tube you could get all new housing and cables, then re-route the rear shift housing to enter the left side inlet. This would be a much smoother angle for both front and rear shifting.

I also noticed that the hydraulic hose into the rear brake is pretty awful. Usually you can loosen that banjo bolt and turn the housing forward so that it isn't making that >90 degree turn. Don't loosen it too much or you will lose fluid; just enough to rotate it forward.