Calisun
In my opinion, quote "my opinion", if someone will use RTD or Re-entry permit, yes, that will raise flag when you request a visa from your home country embassy. The reason being, both of these documents have your country listed on them. Once you become a US citzen, you'll send your US passport to your home country embassy and that shouldn't be a problem. At that time you'd have given up your previous citizenship and you'd be a proud American which will put things in a whole different perspective.
My suggestion, if someone has to go and have a valid reason to go back due to a genuine reason, he/she should renew his home country passport and go straight from US to his country without trying to trick USCIS. If asked then you can show them proper documentation to prove the dire need to go back home. The other two things to keep in mind besides being honest are;
(1) Keep your trip as short as possible
(2) Try to avoid going back right after you get your GC
I know that we should try to avoid going back at all costs, if possible, but If I had to go back this is what I would do.
This is my personal opinion and I know we all think differently when it comes to this issue.
Best regards,