What approach were you going to take on mixing the two. Are you going to take the Arthor C. Clark approach of any tech that is advanced enough becomes indistingishable from magic. A great example of this were the techno mages in Babylon 5. Magic is not really magic but advanced science. Angels and demons turn out to be aliens - possibly extradimensional - but not supernatural. Everything has a "rational" explination. Or, are you going to go the rout of science and magic are two completely seperate entities that are in opposition to each other. Arcanium was a PC game that had a great backround theory for the game itself. As one introduced more magic, mechanical principles started to become more unpredictable (friction, inertia, amps, etc...) thus your character could either go a magic route or a mechanical route - the two together were not a good mix. Finally, a world were magic and science are different from each other, but very compatible. Magic can be used to make technology more potent and science could be used to better understand and utilize magic. There are many anime comics where this is the standard - science and technology completly mixed together.
This is a very cool genere to explore and if done well would be outstanding for an RPG. This is also probably the toughest to do well. The volume needed to properly cover such a setting would be huge. Rules for spells, computers, nanos, aliens, combat (magical, melee, ranged, vehical, mounted, urban, high tech, low tech, medium tech, cyberspace, psi, zero gee, did I miss any), spying, cultures, space travel, alternate dimensions, cyborgs, economics, genetics, mutations, professions, robots, AIs, Golems, zombies, sharks with magical laser beams coming out of their eyes, etc... Don't forget the huge equipment list, spell lists, and "monster" lists. Make sure that the rules are simple, realistic, flexible without being easily breakable, and fun. Now add all that and remember to keep it all balanced to avoid tempting the munchkins.
You would be my hero (and I'd pay money for the product) if such a project were brought to completion.