You do NOT have to care about that at all if what you are doing works for you. I would also assume that using fingerpicks on a nylon-stringed guitar would not really be all that great - nylon strings are valued because of the incredible dynamics available as you use your nails, fingertip flesh, and combos of both to sound notes. Having fingerpicks eliminates that - they are big and loud for steel string use, which is great - but that is a very different thing.
But that is a non-issue for you with regards to fingers. As for a thumb pick, again, not Flamenco and you would lose some dynamics, but do what works.
So that is a way of saying: do whatever keeps you playing. If you decide you are committed to learning a formal style and/or sticking with nylon strings, then you may need to move past use of a thumbpick but that is your call…
It seems to me that you are not interested in adding anything artificial to your nails, but you might find what James Taylor does interesting. He has a few guitar lesson videos on his site. Click on the one called “Nails 101”. He does his own!
I don’t know if this would work for you, but I always notice that my nails get much stronger when I’m doing a lot of typing. The nails have to have grown out long enough to hit the keys. Maybe something about the continued stress “signals” the growing nail to get stronger?
I take 15,000 mcg of Biotin a day, and it really helps with splitting and breaking. But understand that the nails will strengthen as they begin to grow, so the Biotin will have no effect on the nails that have already grown out. This may take months.
if what you are doing works for you. I would also assume that using fingerpicks on a nylon-stringed guitar would not really be all that great - nylon strings are valued because of the incredible dynamics available as you use your nails, fingertip flesh, and combos of both to sound notes. Having fingerpicks eliminates that - they are big and loud for steel string use, which is great - but that is a very different thing.