MoM, to the uninitiated, is Master of Magic, a game I'm always singing the praises of. It's Civ with magic. That's pretty much the shortest statement one can make that adequately describes the game.
I'm not too sure how many turn-based strategy games are out there that involve intergalactic warfare as opposed to just the regular international variety, but I figure there must be a few because of how easy it would be to knock the classic system up a notch. Instead of towns/cities, you have planets. Instead of units of spearmen or phalanxes you have units of cruisers and starfighters. Instead of monsters, you have space monsters (which are a lot bigger). Instead of dungeons and other cool shit, you have mysterious space phenomena that can be explored. And finally, instead of a boring 2D map you have a 3D map which picks out planet coordinates and does all that calculation mess for you when figuring out distances. You could link planets together with space-gates, which can warp ships from one side of the galaxy to the other (like roads). Pretty much anything you could have in Master of Magic could potentially be translated to space with the scale of it boosted appropriately. Why rule one world with your powers when you could rule many?
So, in a sense, this could be the sequel to Master of Magic. After ruling the twin worlds of Arcanus and Myrror for many hundreds of years, your legions of loyal followers have progressed and prospered in the peace resulting from your ultimate leadership to the point where they can now construct starships and the like, and Arcanus as a whole becomes your first "town" on the galactic map. What next?
Well, your power reserves can now be powered up by tapping planets and become even more powerful - able to reach the furthest areas of space. Other planets tend to have one or two races controlling it, and taking it over adds to your army power, food and cashflow. These planets often are primitive or at a technology level far below yours, in which case you can use it for food or mining production. If they're around the same technological level, however, you can use it to build new ships.
Like the nodes of the previous games, jungle planets (earth), nebulae (sorcery) and stars (chaos) can be tapped for their magical energies, but you'll need to defeat the local beasties first. This can be done with the traditional MoM battle system, sending in smaller units to empty the place of danger before a magic spirit can be melded to it (which can safely travel through space like it could over sea and land).
As well as smaller units, you can produce certain larger units too. These will mostly be things like cruisers and starships which can transport smaller units between planets. Some of the summoned monsters will be colossal larger units though, and will be able to enter large-unit scale battles. For these guys I was thinking of something like Lovecraft: huge monstrosities that float about space and are maddening to look at. The large-units would appear with the smaller units but look much bigger than them, since I'm pretty sure modern turn-based strategy technology can handle having titanic-sized units and small units on the same screen.
The spells are all accounted for. Most will be changed to reflect the larger scale, so city-spells will now be planet-spells. Summoning spells can produce both small and large units. Your enhanced powers will allow you to fire spells halfway across the galaxy, like how you could do so from half a continent away. Since most of the regular scale battles will still exist, most of the spells are still relevant too. Of course, there'll be several new ones especially designed for outer space exploration: maybe a spell to allow normal units to travel through space quickly, or a spell to summon a black hole next to an enemy planet (which would work like Call the Void) to throw a spanner into their gears.
I dunno how amicably the high fantasy and sci-fi worlds could be merged, but when you consider similar attempts have been made in the past (take the D&D module of Spelljammer; a sort of fantasy space-faring system that uses the d20 D&D rules) it could be pulled off if we keep space as interesting as what's going on planetside. For instance, the Myrror version of space could be a lot different from the outer space we're used to...
Nothing too radical would need to be changed about the core gameplay, and with this you'll be able to load old save files from the previous game and let those powerful wizards have a whole galaxy to conquer. Alexander wouldn't have needed to weep about having no new worlds to conquer if he had figured interplanetary travel out in time.
