Incorporating a system where your versatility can increase with the more experimentation. This is kind of based on Jared from Plat who was a master of all the mechanics in the rogue facility. He knows all the builds in and out and was able to come up with a lot of interesting things.

I feel it would be a really fun thing for the player to be able to more easily switch between two sides of a coin as far as training. It may be pricey or temporary, something which might require a cool down or something to inhibit it from just being a switch going on/off at will, but something to make either build more like shifting a gear.

For example a certain garment that allows you to have a temporary build built from scratch that will wear off in a certain number of hours. Or a once a month switch feature where you can choose between those builds you have stored to be able to activate when the month is up as part of the BOOST system.

A multi-faceted ring, on each facet you can assign all of your PTP/MTP. Once per (day? week? month?) you can rotate the ring to a different facet, and its an instant/FixSkills level migration speed.
5000000 Reim scrip... to buy, and per additional facet. (Ring comes with two [2], so when you wear it how you are trained now gets recorded, and you can set the other facet. :)