Believe you me, NSI is NOT the culprit, YOU are the cause of the problem.
It is distressing to see so many new techs blame products, then bad mouth that company or product when in fact, it is the nail tech techniques that are causing all the damage.
If you have had correct training either with NSI or another source, you will have been taught how to remove a BUFF off gel correctly and one of the biggest technique taught is, to always leave a thin layer of gel on the nail and it will grow out or lift off in it's own good time if no other product is applied on top of it.
If you are wanting to apply another product (even if it's acrylic and not gel) leaving a thin layer of the buff off gel on the natural nail will not affect the new set, providing you as the tech have done all your prep correctly that is.
The ONLY way your nails can become thin is due to being filed that way by YOU, either during the prep stage or removal stage, NO gel thins nails like you are suggesting.
One saying that Greg from Young Nails says and I think it's one of the best is "It's NOT the tools that do the damage, it's the fools that do the damage".
You say you were only taught in college to remove soak off gels, maybe you need to return to college to learn how to do buff off gels CORRECTLY.
Please do not blame NSI or the Balance gel system for a problem YOU have caused, just learn how to work with buff off gels correctly and the problem will be solved.
Sorry but this is harsh, I hear what your saying but the OP was just looking for some advice which is what this forum is for, there are certain ways of giving that advice and being shouted at isn't the way. The OP is new to the industry and is still learning, she is trying to understand and rectify the problem that's more than can be said for some tech's out there. Let's not scare people off from asking questions as that would kinda defeat the purpose of this forum.