I have a rather simple, but as far as I know, new idea. However, I don't know what it's worth. It's about Lie algebras. I once hoped to shine some light into the classification of non semisimple Lie algebras but I haven't found a good key. Only many, but none of which opened actually some interesting doors. I still don't know whether I wasn't able to see the interesting stuff or whether there was none.
But you see, this answer depends on how you like Lie algebras, the algebraic part, not the analytical, although I suspect there is one, too. Hence I will have to ask: in which area are you searching for an answer. Pure mathematics is still very broad,