https://game.watch.impress.co.jp/docs/news/1117159.html
First info...
They decided after doing the last 3D Classics wave, it would be a waste to just leave it there.
Alex Kidd was chosen because of how popular he was on the Virtual Console in Europe...it's likely they will continue to use data like that for deciding future releases.
Gain Ground won't be the only arcade release. There will be more.
15 Titles is the start depending how well it goes they will do more.
There will be Saturn and Dreamcast titles in the future as well, if it goes well beyond the first 15 games.
Rieko Kodama is a producer on the new Sega Ages project...