I think that is a sound approach (but I am no embedded developer, so...). Changes should be based on trunk either way, you can also send a patch for 15.05 upstream but trunk is what you need to aim for. Only after that's been accepted it makes sense to also send one in for the stable branch.
Git is recommended (also use git send-email to send your patches to the mailing list).
The wiki has instructions on how to boot a ramdisk image. should work on ar71xx as well it seems. However the instructions talk about the WNDR3700 so I don't know how to proceed further.
When googling I see some links pointing to an image like this though, to boot from RAM:
https://downloads.openwrt.org/chaos_cal … e-lzma.bin
Maybe that helps?
(Last edited by Borromini on 4 Apr 2016, 21:56)