I work as a repair technician, and on one of the machines that I maintain there is a transfer timing belt. Over time the timing belt gets beat up so inevitably we have to change the old belt with a new belt. Instead of us taking the entire transfer unit apart (which takes six hours) I want to cut the old belt and splice the new belt to the old belt so I can fish the new belt through the same path the old belt takes and cut the old belt off the new belt and splice the new belt to fit onto the machine. Sounds complicated but it is much easier than dismantling the entire transfer unit which (did I mention) takes six hours. I know there are splicing kits on the market but none for timing belts, can anyone help me.

If this was a chain, I'd say give it a try because some Mercedes techs used to do this and be completely successful.
But a rubber belt? I'll chime in and say no way would I trust this as far as I could spit.
Ya just have to bite the bullet on this job sorry to say because of what you said here:
"Over time the timing belt gets beat up so inevitably we have to change the old belt with a new belt."

Think of it as "job Security"

And some O/T... Thanks for your opinion!!