EoSD needs no EoSD-like sequels, end of story. Sorry for the people who like this game, though.
I think that it'd never happen.
but if you want speculation... I want a sequel to one game have a sequel to all the games where each stage has a different scoring/lives system and the midboss is the extra boss of that game and the endboss is some new character we haven't seen around (e.g., a 3rd Moriya Shrine god, or Satori's other other sister, etc.). The extra stage is of course PoFV style against all the original final bosses in a row until you beat them and then HRtP style against
I'd like a game where grazing makes you lose points (1), being invulnerable while grazing makes you lose even more points, trying to memorize stages and boss patterns would eventually get you killed because the stages and bosses would use different attacks without any warning at any given point in the game (2).
(1): could be done by having a temporary multiplier in the game (as in, they don't carry over stages and can be lowered during stages); grazing would lower it
(2): even if the attacks wouldn't change, the enemy movements could be more random or depend heavily on your positioning and timing (for example, far away enemies shooting at you could force you to dodge at different directions, which would in turn affect the enemy AI's movement and/or their shot timing, in a way that makes it difficult for two runs to be played the same way)
(3): (1) and (2) are my attempts to give some sense to my own joke ideas.
Alternatively, make said game with Touhou scoring mechanics medley and mess them up like, (a huge battleship Touhou Arrange Modes is approaching warmly)
- for EoSD, since it emphasizes grazing so much, make EoSD have unlimited extends at each 10m (more for higher difficulties), but per-frame rank increase based on current lives; bomb amount wouldn't be changed when you die (maybe you would gain one bomb, since there would be people playing for survival also), graze would give more points during stages and none at end of stage bonuses
- for MoF, whenever you have full power up, you gain ((current faith counter * current lives/max lives) / some factor to compensate for 999.990 faith counter at max lives) points per frame (except during midbosses/bosses), but the faith counter doesn't carry over through stages (the shining point items and the faith items that replace power items when you have full power would remain as they are, for added bonus)
- for SA, have enemies shoot faster and more while the tension gauge is on, which helps you graze more (and remove the grazing while invincible) and maintain the graze meter. Graze meter would work as a multiplier applied to enemies and affect the amount of point items that they drop. Point items would help maintain the graze meter. (at times, going to the PoC would help initiate a multiplier session if there aren't enough bullets to fill the graze meter)
- for UFO, make UFO takedowns not remove the bullets on screen, and have the player summon each of the three UFO types (not counting rainbow) once, fill them with enough point/power items, destroy them, and then have the player summon, fill and destroy the Rainbow UFO to enter X-Medal mode (lol), where you don't summon UFOs anymore, but instead each UFO fairy releases not one UFO tokens, but three rainbow UFO tokens; collect three of the same color to make the UFO tokens' value raise; the chain resets once one UFO token leaves the screen (Ichirin, Nue and Nazrin would give lives and bombs as usual to compensate for the lack of UFO summons). At a point, when you have maxed the value of UFO tokens, you wouldn't need to chain them and can collect them more freely. (alternatively, to raise the value of UFO tokens, it could be required that the player has collected all of the UFO tokens on the screen first, like in the Raiden Fighters series)
no ideas, for now, about the other games.