The simplist fix is to:

-Raise XP gained per synth. ( I would suggest by double, but thats just me )

-Have earned crafting abilities effect the synth with a greater posotive reaction. (we earn thos abilities, and put them on are abilities bar so we can use them in the crafting process, now give then true usefullness and value)

-Raise the effect of various colors of stability. (giving the "wait" action more value, and alow certain earned abilities to sooth the reaction of the synth, thus givingus more control over reigning in instability,)

These few seimple chages would involve the player more per synth, and if they just give them a healthy XP boost so you can atually se your XP bar move after all that effort, you feel like your getting somewhere.