Upgrading Angstrom manually


i have a couple of BBB running Angstrom (custom built with bitbake).
I’d like to upgrade these devices. They do not have access to the net, but they have access to our intranet. and i can send them custom commands and files.

I see two possibilities :

1/ Bitbake a new image. Upload the new rootfs to the BBB and make it extract the rootfs, overwriting previous files.
2/ Bitbake a new image. Upload all the generated .ipk files and run opkg on the system. Although i’m not quite sure which commands i could use ? Uploading everything in the same dir and run opkg *.ipk ?

I feel like the bitbake way would be the cleanest/easiest way. Especially since later on i could just upload the ipk for just one software update.
and have the system “in-sync” .

Is there any information on the opkg storage system ? Basically i’d like to bypass the opkg update command, and manually put the packages in the store so opkg upgrade would pick them up.