If im not mistaken its only like 2.5k pkp/ring. Which is pretty much 6 wildy skot rings which is kinda achieveable.
Option 1: If they however add an extra way i'd rather see it happen through pc and a rather high amount of pest control points
Keep in mind its not really the dagannoth rings, but mainly for ring of suffering, imbueing the ring of suffering in pvp causes it to be dropped on dead.
(Which is a good pkp sink for pkers and is one of reasons imbue scrolls hold value)
Option 2: Optionally they could also add another scroll to the slayer store which would be significantly cheaper just for the dagannoth and maybe even wildy rings (For like 550 slayer points, like ring of wealth scroll) And could disable the option for ring of suffering.
Option 3: Could also make it a possibility to use click a ring on a slayer master to imbue it for 250 slayer points (As it wouldnt become an extra tradeable eternals could farm with slayer point stacking, Its also similar to the pkp imbueing on that npc.)
Long story short: I agree that it could be challenging for some modes to get imbue'd rings, but rather see an extra active way rather than an AFKscape type of addition to the game.