Duplicate Router Web Interface with fewer Permissions

I want to make a lighter duplicate of an web interface of my router (Dovado Tiny AC) with fewer permissions. This lighter interface should just use special functionality which is sadly not supported by the routers API.

So i thought to get the data from the web interface with a little proxy server bypassing the cross-site-request problem. But how do i log myself into the routers interface from a different site or run js-functions on the routers interface like "search for available wifi-networks to extend". This would be cross-site-scripting, how can i bypass this?

I understand, that this is blocked because of security concerns, but in this case cross-site-scripting is needed for legal purposes as explained.