You would have to do a lot more than hack it. You would have to cut, split, deliver, and stack it .
The most basic reason you can't have more factions has been mentioned in these threads before: Binary Numbers, as in decimal 7 = 111 binary. Only three placeholders for faction IDs. There is a zero placeholder, 000, and it is Planet. You would have to force a fourth digit, 1111 binary, or 15 decimal, in order to have more factions in play.
The system would have to keep track of all those additional bases and units. Not a roadblock, but a lot more complexity in their reaction and interaction.
You have a lot more than double the overall complexity, though.
For one example, the game would become quite a bit slower with all the added diplomacy as the turns pass, and all the more so after all Comm Frequencies have been revealed.
With 7 factions, you have 6+5+4+3+2+1=21 pairs, with 42 paths. In single-player, you control only 6. The system has to control the other 36.
With 14 factions, this grows to 13+12+11+10+9+8+7+6+5+4+3+2+1=91 pairs, with 182 paths. In single-player, you control only 13 of these. The system would have to control 169 paths , almost five times the current number! (edit: math)
Imagine how much longer a multiplayer game would be, especially PBEM, with 13 people to wait for!
Also, what size map would you propose? None of the standard sizes would be anywhere near suitable for every faction to have half a chance of surviving beyond the first 100 turns, if that long. At least half would be eradicated one way or another by then. It would require huge maps of at least 256x256 to give them all the slimmest of chances. More than 500x500 would be needed for epic-length massive-empire-building games, although I would love that option for such humongous 500x500 (or 1000x1000) maps now.