Hi Gurus / fellow immigrants.. need help with the acute position my friend has landed myself in.

Situation is like this:

1) Current H1B getting expired on 30 September 2017
2) H1B amendment (Client XYZ) + extension application filed in May, 2017. (the time he was supposed to file extension, his contract with previous client came to an end. So he waited for new opportunity with XYZ and then filed for extension + amendment, hence missed the premium processing deadline)
3) RFE on the above application issued on Sept 25, 2017 (not yet received) - so don't know what is that USCIS is asking for? Though from past experiences it should be client letter. Which shld not have been a problem but....
4) he has resigned from XYZ a week ago and looking forward to join client ABC at different location)

Now the problem is how to proceed in this situation.

He cannot go back to client XYZ and ask to revoke my resignation till my RFE is resolved and Visa is been approved.

Q: I suggested to file new i129 form (extension + amendment) with new client ABC without replying on RFE received on application with client XYZ..? As his stay is legal wrt to earlier application he filed. So now with change in employment and location - he need to file new LCA + i129.. that he can do referring the previous application number and file a new i129.. but i am really not sure about the legality of the suggestion.

His visa set to expire tomorrow 9/30 - so don't have anytime to file new application before his current visa expires. And If we opt for above- would that be legal?

Really stuck, will appreciate if anybody has any experience / knowledge as what best we can do? and the validity of the path suggested in Q?
He has only 2-3 days time to make decision on the same. (as soon as i got time from my office - i am posting here with great hope)