I'm just throwing these out there as random thoughts 15 minutes after waking up - they may no longer make sense to me this afternoon ;)
Start all thief skills at a base difficulty of 8 - except Climb walls, which would start at a difficulty of 5.
Two skill points to distribute at odd levels (including first), one point to distribute at even levels (this is totally just woke up guess work - I suspect that would need tweaking).
This would allow for the DM to actually set difficulties for the different tasks depending on the situation.
Lets see if this still makes sense when I am fully awake ;)
Succubus Sunday - Source
2 hours ago