I would not:
1) Go to oxen blocks. There are many reasons.
2) Go to a self tacking just to solve jib sheeting. If you want a self tacking jib, that is anouther story. By the way, the 6.0 points a lot better with a non-overlapping jib. Borrow a H16 jib and try it.

The easiest way to solve the problem is to mount additional cleats on the shroud chainplates. It is easy to cleat and uncleat from the wire. Adjust the block cleats up as high as they will go and take the fairlead strap off. This is for when the crew is on the tramp. I would also get rid of the six-way wire across the tramp and replace it with rope loops in the tramp.

If you decide to go to a self tacking jib, the original 6.0's system is not great by today's standards. Look at the Tornado and F18.