I mean just use the advantage of new technology to fill up the gained space with batteries. The premise of limiting RAM is also pretty much BS - if I get a device with 16GB RAM I still get the same battery life as now, but if I put more memory inside, I do this willingly to sacrifice battery. NOTHING CHANGES for people with 8/16GB configuration.
Unless they're doing this with the classic Apple smug "we know what's best for you" reason. Oh and to sell more adapters.