The amount of work you need to bring an Android device to a modern version is very, very big.

Does a new kernel version work? (Android will require it). Will the device drivers work on a new kernel version? Will driver blobs be compatible?

Chipset manufacturers will definitely not send you a new version of a driver if you're not the mobile manufacturer (and sometimes, not even if you are). You're on your own, updating the driver, or writing a shim that acts as a proxy between the driver, kernel, Android, etc. It's just not feasible.