I've also been wondering about a mod like this. Agility would be really fun. Kinda like a Batman/Spiderman thing. Where you could just jump/climb up a building instead of trying to run away from them on the street. In any case, I found out that you could actually change the maximum height at which you climb a climbable wall. I set Max_climb_height at 1000. the default is 3.15. And there's this one spot in particular that I look cool at when I'm climbing. I also increased my sprint speed, so in the video, it might look legit.
(Btw, I did the modding in tweak_tool using
bojan's SRTTXtblEditor found here:
http://www.saintsrowmods.com/forum/index.php?threads/xtbl-editor.238/
Trust me, when it comes to modding the tweak_tool, bojan's xtbl editor makes things MUCH easier to read! Thanks bojan!