A System/Stats Nen
Would still have to be nen and follow the rules, including some impetus for why he got such a nen ability in the first place.
Like “A desire to measure everything in numbers and the necessary understanding of the basic calculations required for the system”
(quoted from wiki: Biscuit Krueger became capable of altering her appearance without actively training for it, instead wishing for her body to change for years, which caused the changes to manifest little by little.)
stats
- his attributes when he’s enhancing himself with nen (includes anything he can enhance... strength, sight, regeneration, constitution and maybe mind. Plus more)
- his proficiency with the 6 categories of nen
NOT his normal body, that’s trained normally (because that would be way too OP)
System
A system would obviously not have quests either, though he can be rewarded for following his own nature or wishes to a small extent, but not any outside rewards.
Exp. would be literally experience(learned wisdom) or, obviously, come from nen/blood sucking, with increasingly hard level quotas (exp. per. Level).
No idea what levels will do though? adding stats/attributes isn’t logical unless it’s levels in that specific area (levels in enhancing for example), just increasing your nen reserve sounds plain because the increase can’t be too big.
Skills
“Skills” will just make it easier to record/remember his abilities but he can still forget (or use skill-slots to limit the currently active ones) or skills can be something similar to Chrollos ability. Just make sure you nerf them if he can use them all at once, like having to kill his victims AND/OR weakening the technique or reducing it down to its main component (“the bombers” power becomes just a “time bomb” or “little flower” becomes just an explosion without protection for the user) AND/OR use skill-slots with big abilities taking multiple slots.
MY OPINIONS :
- “Skill stealing” works best on its own or maybe with stats option(1).
- Levels works nicely with stats option(1). Note: enhancing only, he’s on his own for the other categories.
- Stats option(1). does the trick with a few trainable attributes (Transmuter—>lighting nen & stretchy nen = shockingly stretchy nen), (Conjurer—>nen sword & haiku effect = sword inscribed with ???) Etc...
- “Skill memory” with skill-slots and no forgetting is also a perfectly independent power, especially if the conditions for moving “skills” to & from slots is thought out and interesting.
- Stats option(2). (My Favourite) works best alone but it doesn’t matter if it’s attribute/stat points or levels. The “specialist” category indicates his understanding and proficiency in combining the other 5 categories = creating limitations and advantages. (“skill memory” works too, but no “skill stealing” without a limited “skill” for the specific task. Best without “skills” in my opinion).