I don't even think it's accurate to say Mr. Paradise and Amiya occupy the same niche. Amiya specialises in IBM PC DOS, obscure stuff that interests her and Windows games from the multimedia explosion period (i.e. Windows 9x), which often have unclear legal status. This niche doesn't overlap with DOOG's but PC market of the 90s is a nightmare as far as permissions go because cost of entry was significantly lower than on consoles.Amiya's content is based on old games.
1- holo has that niche already covered with korone
2- holo has way more restrictions on games, that would only sour her experience. Now that she's indie she's also able to use emulators if she needs to, imagine trying to do that on a jp corpo.