Interesting. I'm 6'3"/205(ish) and have larger hands than most people I know. The G19 and pistols with grips of similar length (CZ P10C, S&W M&P 2.0 Compact, CZ P07, etc) have never struck me as being too short in the grip. Indeed, most of the complaints that I've heard about G19 grips over the years are that they're too big...
In any case, couldn't you just load a G17 mag into a G19 and use the mag itself as something to rest your pinky on? That's what I've done with my G26 for years.
Not trying to pick a fight, but it seems like there are a lot of solutions to the grip issue... and the G19X is the solution that makes the least sense to me.