There is a very simple solution that wouldn't ruin the market.
Atm we rely on vanilla enchanting with some things removed.
Why not make it a spell?
in /gamemode 1 on vanilla creative mode, you can say /enchant # and it does it
you make that the spell and only give certain ones
as for ruining the market, that is where xp comes in, if DS takes 1000xp from me and I lose a whole damn level and can't make any more till I hit 60 again you better believe I'll be charging a lot of money for it.
The more xp you make something take the less people will do it and supply and demand will take care of the prices. All you have to do is apply the change and monitor the market for the avg price of said enchant over time. If it goes up, you made it harder, if it goes down just up the XP cost.
I actually believe currently enchants are too cheap as the market is flooded. Changing away from vanilla enchanting coding gives more control to the mods on the market.
Years ago a e4 unbreaking pick was a very expensive thing, and prices on other goods were higher as a result. We had an economy where everything had a value. Now most common items aren't sold by merchants nor put in the market so they don't really even have a value.