This old house keeps on surprising me… question about multi-layered roof

Just took the unused chimney down on my 1863 colonial and discovered the previous owner (who once told me he was a roofer) just kept layering over the old shingles.

The exterior layer is in ok shape but pushing 20 years. I’m planning on installing solar panels in the next year, I think I know the answer but: should I have these pulled and reroof before?

Thanks for any advice.