Modify or rebuild?

One year after my first real build, my linear bearings have arrived!

Now the big question: do I modify my existing machine to use the new bearings or build a new structure from scratch?

The new rails for the x-direction are a bit longer than my old travel and certainly have a significantly taller profile than a skate wheel. If I just mount these on the front of the x-bridge structure, this will push the z-axis structure even further forward. If everything was perfect, this wouldn't matter however any wobble in the bearings and link to the x-drive will be amplified. 

One solution would be to try to move the x-axis motor and bearings forwards but I would have to modify the wooden structure a bit for this. 

The alternative is a major rebuild with a new design to make full use of the new bearings. This is possible but then I need to work out the new design properly and ideally I'd like a CNC machine to get all of the holes etc it the correct place. 

The third alternative is to have a half way mod to the existing machine and hope that the resulting tolerances are significantly improved and good enough to allow me to CNC the next gen machine :)