DNS Problems with Mobile Data

[biketool]

How large is it to cache and update a DNS server locally?

Just cache?  Not too big.  Easiest way is probably to flash OpenWrt on to your router, as it's built in there (among many other great features, and more standard Linux experience).

The OG WRT54G Linksys AP came out a year or two after y2k... 
But yea, there are several components that we need to bring into Mobian; at least optionally, probably any component we can bring over as a package for road warriors.
For me at least, my mobile phone and data plan IS my router at least 50% of the time when I do not have a trusted network connection WiFi or a network cable.
Ideally mobian would make it easy for a user to use customized DNS as DNS is an easy failure point where freedom and privacy can be attacked.