Also, I really want an evil male protagonist as a proxy to play as, so either maybe turn the male protag evil via an evil seed or have a new male protag who finds out about the two /three Exstia and their sexual arrangement with the original male char and wants the girl and the world for himself thus he wants to turn them + the Hakase and the so-called rival girl general Asarin, evil and obedient to him.
I actually would like to see the MC getting an evil route (Partly due to him being so plain that I think even NTR fan would find no fun at all when bad things happen to him and partly due to the villain being equally plain). The game also really makes me interested in the corrupted heroines not joining the bad guys, but instead be the third faction fighting both the hero and villain.
Maybe in the next game, they could have the heroine get corrupted due to jealousy as the main reason and goes "Screw the world, all I care about is my boyfriend" (Basically, going all yandere) and you can decide to be evil with her or not. In Mahou Shoujo Nao, we got corrupted heroines being friends with each others. That's fine and all but I still would like to see the corrupted heroines being rivals, each keep trying to gain the MC's favor.
That could be the plot of the "Evil route" in the next game. The two heroines from previous games have been corrupted but they hate each other's gut so the MC has to get them to work together while he corrupts the remaining heroines.
As for the game itself, the corruption is good. I really love the corrupted forms of both heroines (Marina's is better in my opinion). Then again, it's Inoino so that shouldn't be a surprise. However, I feel like it's not much a corruption game but a nukige with corruption endings. I guess it's because the corrupted heroines don't really do much. It's just two H-Scenes then game over (Kinda like most Inoino's doujin, actually). Also, like you said, no routes with both heroines being corrupted. So, overall, I think it's good but I also think it can do a lot more. They should get rid of the gameplay as well, in my opinion, it's really uneccessary.
As for Wizard Links,... I don't know, it doesn't seem really interesting (That Olfena girl looks really cute, though).
I know these are not the exactly the same genre but they have some kind of "corruption" too and look good.
http://www.getchu.com/soft.phtml?id=878751 (BISHOP is my favorite brand) I miss MAIKA :(
http://www.getchu.com/soft.phtml?id=860989 (This one looks pretty good)
http://www.getchu.com/soft.phtml?id=879392 (I don't know if this one is going to be good or terrible, i'm not a fan of hardcore violence in the CGs but the character design looks good)
The second one looks like it has potential (However, if that black knight guy is supposed to be the MC then I think he's too "edgy).
Shine