With 1 wpf its way inaccurate to be used for great effect,
respectfully disagree. I have tested it several times. Recently, I was playing with my alt char (2H + a few points in throwing), grabbed a "sniper crossbow" and some steel bolts from the floor, and took up the same position that I often take with my main char (>130 WPF archer with triple-heirloomed warbow...). That castle with the flag in the middle on top of the building with the long winding stairs around the building.
Mid-range shooting on moving targets on the outer wall - there were just a few bolts left, but I had 60% hits and 2 kills. Definitely better than most reasonably skilled archers will achieve in that position.
The only thing that is a real pain with 1 WPF is not the accuracy, but the reloading time, that takes half the round... ;-)
So xbows are exactly the same that they were in reality: a very efficient and accurate weapon for peasants and other skill-less bastards.
In the middle ages there were actually discussions to ban that weapon, like we today talk about cluster bombs and landmines.
So: xbows ARE a pain in the ass, and we have to cope with that. Only thing that I would suggest is a great idea from another thread: make upkeep costs depend on WPF, so if you use a weapon that you have no skill for, it will more likely break and be more expensive.
Tthat would limit the xbow-sidearm plague a bit.