arbiter,

GC process is long and will go well beyond your OPT and H1B process. Even after your LC is approved, you need to maintain your non-immigrant status. You'll be continuing on F1 or H1 or any of the non-immigrant status until your I-485 is approved. So a petition for GC alone doesn't change your non-immigrant status, yeah though filing for GC while on F1 might mean that you are changing your intent, it neither hurts your GC nor your F1 is jeopardized. Also once your H1B is approved, you will be on a dual intent status which is definitely better than being on F1 for a GC process.

The problem I see about the intent is for your F1 status in future just in case your H1 is not approved. In that case, you continue on F1 and become eligible for OPT again some day. Now if you apply for OPT while your GC petition is still pending, your application for OPT might be denied on the basis of intent as you have already expressed your intent for settling permanently in the US. Also, you might not be able go out of US and return on F1 while any of your GC petitions is pending unless you have your Advance Parole and EAD. Besides that I don't see any problem for now.