I love have the OSR Stats and i don´t even use OSR Systems. I use World of Dungeons and Ironsworn, but being OSR a simple system largely know is easy to transport to any other system.
That said i think that is better to pick any system and go with that information because made the sheets print and ready.
From a Marketing point of view i definitely will go with ShadowDark. Again i don´t know too much about ShadowDark, but from the data is today one of the most selling product and you could approach most players.
For last i didn´t knew you asked about the hexmap, but one suggestion i try and worked for me is using only 1 by 12 hexes per map. I found it an approachable size and i can use a d12 for a linear probability or 2d6 for a curve probability. I use 2d6 for a more centralized zone (example around a capital city) or the d12 for one more descentralized (example an island zone).
Hope it helps at least for some brainstorming and sorry for my English. Not native language.