Ok, I get the issues.  As for his position within the college, it is more of an "outside the normal structure" kind of thing.  If you don't want the college being fleshed out yet I could go with the second idea for after the cave collapse.  Instead of what really happened his master died in the cave collapse and after Chrollo's escape he didn't return to the college.  I could probably think of a reason he would be helping the rose knights.

Instead of that, I could merely lower the rank of his master to something of a "head of a department".  That would lower them both down in importance, and avoid touching the main NPC's of the college.  Also in regard to the "power-hungry and outright violent", I wouldn't consider Chrollo to be the first descriptor.  He has no real need to climb the social or political ladder, and most times couldn't care about rank.  And for the outright violence, he is leaning towards a lack of inhibition.  He doesn't seek violence or instigate much of it, but you will probably not find him actually monologuing on the merits of pacifism.  If in his personality it came off as either of those I can change it up.  When I was thinking of his personality I took considerable inspiration from Pariston in HunterxHunter if that gives any good context.  I can change the very end of the history if it was giving off that impression.

Ok time to tackle the big thing: Gravity magic.  Ok, so I'm just gonna kinda say most of what's in my head about this and hope it makes decent sense.  So when you spoke of more small-scale and single-target spells, that is 95% of gravity spells.  They can range from changing the weights of objects to manipulating the momentum of a swing.  The only traditional attack spell it has is condensing air with gravity and launching that at people.  All that is the stuff that would be considered low to low-high tier.  Of course, manipulating larger or living creatures take exponentially more mana and concentration.

Beyond that is the range of AOE gravity spells, aka the hard ones.  Using them is balancing multiple very fine lines.  Of course the larger the area the harder it becomes. (while already being extremely difficult)  Another boundary to watch out for is as you said allies.  The nature of Gravity is very impartial, and its magic is no different.  Both the caster are affected in the area just as much as the intended targets.  This makes it a very technical study of magic that has potentially incredible abilities, but a just as dangerous potential for a devastating crack back.  The most powerful users of it (which Chrollo is currently nowhere near) can make multiple areas of effect, thus avoiding themselves and allies.  The ability Chrollo has is to be unaffected by his own gravity magic (and maybe others idk) thus allowing him to avoid one of the major pitfalls of the dangerous field of magic.  An AOE use of gravity magic of 5x5 feet would probably leave a normal person exhausted for a week after using it.  An average mage could probably hold that for 10 min before exhausting.  Chrollo can probably hold the 5x5 for around twenty min.  One of the most powerful mages can probably manage about 10 of those separate areas for the same amount of time.  Any large AOEs attempted by Chrollo would probably only last around 10 seconds depending on the size.  Anything army-sized probably is out of reach of all but the top 2/3 mages in all the world.

As for his normal attacking magic he mostly uses fire and earth magics around intermediate levels.  He could probably manage a high-level fire spell like a fire tornado or something.  These are the spells he would have learned naturally studying at the college.

Thx for working with me on this! I know this character is pretty out there, so I appreciate this.  Also, I'm sorry I'm filling up a whole OOC page with my explanations lol.
[@Raineh Daze]