I filed a patent(provisional) a couple of months ago. The disclosure consist of two parts: 50% description of an underlying technology, and 50% a specific application of this technology. I haven't filed the claims yet. My initial plan is to file claims for the specific application of this technology (that is the real novelty), but not sure whether to claim for the technology itself as I'm aware of similar things, not exactly the same though. I thought to postpone this decision until I get proper advice. I guess I can always file narrow claims for the underlying technology, if that made any sense.
Now I want to file another patent for a different invention that shares the same underlying technology with the first one. The disclosure is again 50% underlying technology and 50% new application. My initial plan is the same as with the first one, in some months time I'll file claims for the specific invention but I'd like to leave open the possibility of claiming the underlying technology if that makes strategic sense.
My questions are, can the second patent claim priority of the first patent, based on the fact that the disclosure is 50% the same (the underlying technology), even if the inventions are very different? If I claim priority but then later on I don't file claims for the underlying technology would that priority claim be a problem? and finally, can priority claims be added or removed by the claimant after first filing?