I tried to TCL my way out but that just makes you sink vertically downwards. I'd like to allow the player to jump, but no other movement controls but I don't think that's possible. I could put a trigger box there, where if the player is in it for a certain length of time it would teleport the player to the top of the steps, but won't that make my mod incompatible with any mod that modifies Riften? Also, I'd have to do this for every area where it is possible to get stuck, not to mention ruining immersion.
Any suggestions how to fix this or get around it would be greatly appreciated.