If they did make a CV1 movie they would have to add in other characters because the film would be dull if Simon was the only hero.
I see this happening for a couple of reasons:
1. CV1 is the most basic premise of the series. It's basically Simon ventures off to battle Dracula and his minions. Basic plots are easy to embelish without crippling the premise through recons. If you already have a story where character relations are strong and essential to a universe's continuity, the possibility to fuck it up is greater.
2. Because CV1 is one fo the most basic stories, you can add a lot to it while keeping the premise the same. As long as Simon ventures into the castle, fights off zombies, mermen and skeletons and main baddies like Medusa, Frankenstein's Monster, Death and eventually Dracula, that's great. You can add some story of him before that, his relationship with "friends" or even info regarding the Belmont heritage/duty. Hell, you can also add on something like Dracula initiating the fight by sending his armies into the Simon's hometown to kill everyone, or even add a rival vampire hunter(or hunters, like the Marcus Brothers in VHD:Bloodlust) crossing tracks with Simon(and probably getting killed inside the castle). As long as the meat of the basis remains faithful to the game(which was as basic as basic can be), it could work.
To me, the more complex an original story is, the more an adaptation can fuck it up regarding continuity or retcons. The more simplistic a concept is, the more you can go crazy with it when trying to adapt it. Basically, there's MORE room for growth.