I presume you have you tried Kiwix? For less than $100, you can install the full Wikipedia (with reduced size graphics) on a cheap Android tablet with a 64GB card. The installation the first time is a little clumsy, but the experience once it's local is solid: http://www.kiwix.org/downloads/.

I don't think "critical updates" are really that necessary. Swapping SD cards a couple times a year would solve most of it. I think it's pretty incredible (and useful) to to be able to have access to all that information for such a low cost even if it's a few months (or even years) out of date.