What I'm wondering, is if there isn't a chip out there small enough to squeeze into the existing Grand frame, that just regulates to a flat 4.2V?
Something lo-fi. No protection (leave that for the collapse spring), no knobs and adjusting, no battery indicator; just a simple primitive 4.2V output thingy. Ideally it'd be so cheap and primitive that if you pushed it too far, you'd fry it or collapse the spring, throw it away and snap in a new one.
Of course it'd ideally handle high current draw, and center around it's adjustability the same way we do with mechs.. variable coil resistance builds compared to VV or VW.
Make sense? One could dream... LOL
You could easily
Kick or
Crown an 18490/18500 in the Grand, or an 18350 in the Mini V2.
I don't have a REO Grand to try, but depending on how long that spring is...
It 'might' be possible to
Crown an 18650 in a REO Grand (I think it's only about 8mm tall) without the Vapesafe fuse by removing the REO's spring. If you didn't mind hacking up a Crown a (I.E. grinding down the contacts a bit) it seems just by looking at REO Grand photos that it might be quite possible to stuff a Crown with an 18650 into a REO Grand. In theory, the Crown would take over the safety functions of the REO's Native spring.
The Crown isn't quite as powerful as Kick 2 (5-15w and takes atties down to 0.5 Ohms) but it can take you up to 5.5v with regular atties (from 1.2ish - 3 Ohms) and regulate it nicely. It'll work in a VW mode from 5-10w (1w increments) or a VV mode from 3.5-5.5v (0.2v increments). You'd still get a regulated vape with some safety features, and unlike the Kicks and Stomps, you can adjust it without opening the mod.
From what I can see on the Mechanical REOs...the main issue with popping in some alternate controller chip is that you'd have to redesign the button somehow...that's a bigger problem than the 'space' to tuck the circuitry. Otherwise a DNA12 chip (if you can find some anymore), or even a helixed pair for 24w would probably fit no problem...
Since Kicks, Stomps, and Crowns don't need 'constant power' and are designed for mechs in the first place...those are good options that are easily implemented.