To do it using 3.0/3.5's d20 basis, you need to steal from a few places. The first is the Wheel of Time d20 supplement, which brings a couple of concepts to the old slots/day casting mechanic that fit furycrafting very well. The second change is to change daily slots to a stamina/exhaustion based system.
The first concept to pull from Wheel of Time is to apply the Element concept to Furycrafting: Earth, Water, Air, Fire, and Spirit become Earth, Water, Air, Fire, Wood, and Metal. This lets you assign an ease factor (based on the feats and 'spells' from WoT supplement) based on number of applications to the discipline, and meshes well with the merit-based changes. Also steal the ability to overchannel (and thereby kill yourself from pure effort in furycrafting, or knock yourself out the same way). This gives you a basis under the d20 rules to stick with classes if you want, or switch to a classless but level/experience/point-development system. It would be very hard for me to fully flesh out the details here, but I'm working on it just for these boards...I'll link my final efforts!