If i may chime in,
This was "kind of" the case couple months ago, where Slayers maturities were bound to the volcano.
It was clear that it was not enjoyable for most of us, and did not bring any additional benefit, since the Slayers maturity already replaced the natural spawn of Khaffashs in PvP (which were my personal hunting grounds, so meh!)
Like it has been mentioned above, the FnF already offer everything the OP suggested.
Besides, Cuhofs will also spawn a mini-boss.
There are only one natural spawn of high khaffashs left on Toulan, and this is the volcano, so i would try and preserve it.
On a final note, since we already have natural mini bosses spawns, as for marauder/slayer/queens, who are above Stalkers, and are not the most hunted mobs on Toulan, to say the least, I would advice to try and let time implement more "Prized" loot before rushing into throwing BIG mobs first.
I Personally would have an absolute zero interest into killing a 3000//4000 HP mob that drops the exact same loot table than a 300 HP mob, minus a few Lv rated drops, such as components and sockets.
So unless there are extremely appealing items up for drops, i dont think that BIGGER and HARDER would be of a general interest, since it would only mean to cycle peds faster, which i am conviced it is what Marauder/Slayer/Queen already provide.
This was my personal take on the subject, not only as refeered by the OP, but regarding the general idea.
Hope this helps,
E~