this already exists/is a (common) possibility; but you’re still restricted by/limited to the existing affixes.
For caster weapons that means non dmg magick prefixes are Mystic %spirit, Stalwart %DA, Aggressive %OA, you have the same chance of getting mystic like you do stalwart, but Decay(dmg) magick prefix has slightly higher chance than the neutral magick prefixes since it’s still a weapon
yes, i linked it earlier too [Resource] Affix drop rates for rare MIs in a spreadsheet
i’m not sure about the complete interaction functionality, because as Norzan said, because Wraitbound of Binding does seem to drop “all the time”, but according to the sheet it should only be around 0.2% of the time, which doesn’t seem to match my own experience either/like Norzan 
(and as i recall Modal said somewhere double rare % chance should be like 1% baseline now after 1.2.1 or something, but perhaps i’m mixing it up with something else)
*i’m not quite sure if Depraved Sanctuary classifies as easy or hard bonus, my guess is “easy” since just 1 mutator layer, but don’t know for certain