I doubt this will be added. Custom enchants aren't even very creative anymore, unless you come up with a different enchant than overused stuff like -Chances to do more damage -Absorption hearts -Speed -Jump Boost -Stealing player XP, MCMMO, Money -Increaed XP drops There are a lot of possibilities with custom enchants, but I'm sticking to maybe for now.
Something obviously went wrong if they removed it, but I'd be up for it coming back, mainly because I don't know why they removed it.
I would totally be up for custom enchants. Some of these even sound pretty fun. The stealing bit would very likely NOT happen though, since stealing IS against the rules.
Well the thing is survival is already overpowered with loads of legendary items and such, adding custom enchants will only "work" if the enchantments are OP and give stuff like Strength or beacon effects, though I do not see any need for this, especially with stuff like Satima's Costume (excuse my spelling).