I hope its as good (
) as your last idea tying it to RDM melee.
I'll humor you despite the snipe, but overall, it's a bit drastic given SE's current state of do-as-little-as-possible.
Basically revamp all enfeebles to function like DNC steps or TH building with RDM being the only class able to level them up through repeat casts. Something like Slow I would be changed to a default 30% rate with Enfeebling/MND/MACC just affecting accuracy. Landing another Slow I again would bump it up to level 2, or 40% potency. Slow II would start on level 2, but going Slow I then Slow II would take it to level 3, but at a diminished percentage like 43%, up to however many levels SE deems appropriate until 60%, but I'm thinking anywhere between 10-15.
Merit spells would all become scroll learned, their current levels instead functioning as level jumps. Slow I with 5 merits in the Slow category could net a Slow level 6 effect, while Slow II would be 7. Gear that directly enhances enfeebling magic would be a default +1 level. Also, landing a "level up" would add a short amount to the debuff's current duration, that way you're not spending so much time to build it up just for it to poof. Saboteur would still retain its doubling property in this process, only in regards to the debuff level.
Just for you, though, I do want to include a melee aspect to this through the form of a tiered job trait I'd simply call Coup de Grace. 3 tiers, each time you WS, every debuff on the mob is leveled up by whatever tier level you possess. This would allow a RDM to level up a wider array of debuffs more quickly and with greater MP efficiency. Additionally, Enspells can receive a small chance to level up any debuffs of their respective element on-strike, T1s being 1 level while T2s would be 2 on success.
Of course, there's still the matter of enfeebling spells needing greater representation if it is to be the
role and combination debuffs could also be a consideration (like splitting Gravity's -Movement and -EVA as an easy example, but consider something like Bad Breath). I'd also like to see Break be a bit different than Stun, instead incapacitating a mob for a longer duration with a potent -DT% applied to curb kiting or zerg exploits. And I know you sh*t your pants the last time I mentioned Dischord, but the ability to affect a mob's level is something unique RDM could assuredly use on HNM-tier prey.
And no, you'll never shake me from wanting the class to be more melee friendly despite how "fine" you think it is and how that status otherwise translates to community neglect and scorn. Regardless of the fun you, GG, and Cid like to have at my expense, it needs higher utility and some advantages in absence of raw damage. What you alluded to attempts to offer that, just as what I noted above with CdG and Enspells also tries to do.