If the fanbase and market of the franchise is BEGGING for a remake, believe me it will be nothing but healthy for the franchise. Its sort of like a supply and demand thing. If your fanbase is begging for a remake, that means guaranteed profit. As to whether or not they DO remake GSC and even as to what they include in it, or how they connect it to the fourth gen, etc, thats really up to them and what they think will suit the game best.
And I do agree with you on the point of toughening up the gym leaders and such. For the most part, the pokemon fans that have played every generation or who consider themselves "Pokemon Veterans" will more than likely support the remakes. Newcomers, Im sure, might try the remake, but would more than likely just pick up the newest, coolest game. Im sure those who have spent time EV training and improving their pokemon team would appreciate those tougher battles, as they WILL probably be the main market for a remake.
I am personally looking forward to a remake sometime in the future as I did love the Johto region, and it's pokemon.. And I really believe that with better graphics, more bells and whistles and more attention to detail, the story could really come alive again. Whether it be on the GBA (for the sake of keeping the "feel" of the game the same - ie: no touch screen or dual screen features) the DS (to allow connectivity between the DP games) or a NEW handheld console, I will purchase a copy for myself.