The problem may be how would you properly remake something like those first four now?
... Well, I'd at least like them to preserve that 80s/early 90s sci-fi anime feel as much as they can, and III could be made to mesh better with the rest, but I just don't trust Sega as they are now to do a good job there.
*pictures Rhys, Nei, and all the rest of PS2's cast hijinks-ing it up in a Japanese High School*
(Although given their personalities, you could slot them right in with almost no fuss. Rolf takes the protagonists' seat by the window so no NPCs need to be drawn, Nei is the mysterious transfer student that takes up residence right behind him, Rudo is the buddy next to Rolf and constant wingman, Amy is the librarian's aide, Hugo is the guy who only shows up at lunch time and is humorously ignored, Anna is the class rep, Kain is the guy in the automotive repair club, Shir is the athletic girl, Nei-First randomly shows up to wreck havoc and causes Nei to get expelled, Lutz is the old mentor who teaches Rolf karate's ultimate move the Neihameiha Medigo, Dark Force is the evil gang leader, Mother Brain is the dark magic possessed trophy henchwoman of Dark Force who helplessly fights for her master after he is defeated and is the true final boss, the people of earth are aliens from the Algo star system, and the Musik teacher is still gay.)