FF7 wouldn't make a very good mmo, IMO. It's the same reason why "Oblivion online" would suck. MMOs are pretty much 30x the content that are in these games, have proper levelling systems for mmos, have proper ability mechanics, have the proper gameplay, and so forth. And the worlds are pretty much 50x bigger than that of Oblivion and FF7.
By making ff7 an mmo, I'm not sure what your plans are. I'm NOT trying to shoot down your idea, I just want to know why you're trying to make it an MMO in the first place. Why not something like diablo instead? FF7 online will boil down to killing monsters and... well, that's pretty much it. Not only is controlling one character boring since the game is turn based, but there are no mmo battle mechanics in ff7. Enemies don't attack the person who is dealing the most damage, cure spells don't cause hate, and so forth.
Also, I don't think this type of this is possible. If it were possible it would take a crapload of effort, and you can see that I personally don't think the finished product will be worth the trouble. If I wanted to make ff7 online, I'd make a game from the ground up instead. And yes, it would be much easier. Modding ff7 as it is to run online as an mmo takes a huge amount of skill.
To make a good MMO version of ff7, you'd have to code in a chatbox, whisper system, party inviting system, quest system, individually-controlled characters, random encounter normalizing between the three players in a party, new items, multiple parties on the world map at once, vehicle posession, npc quest giving, ability system, new world areas (overworld is puny), scene editing (a huge job for simple difficulty mods, a gargantuanly gargantuan job for an mmo mod), kernel editing (same as scene editing), allowing 1-man parties and 2-man parties, and so forth.
If the ff7 online mod doesn't have these things, I'm assuming it will instead simply be a version of ff7 that lets two friends control your other party members. However, if you intend to do some of the above, and make ff7 an online game rather than a career-mode-co-op game, then by all means. That'd be neat.
Realize, though, that mod-friendly games like Oblivion still have huge trouble creating a stable online mod. I personally don't think even the simplest online ff7 mod would be possible, seeing as ff7 isn't exactly mod-friendly. All that we can currently mod with decent ability is scene.bin, battle.lgp/world.lgp, kernel.bin, and kernel2.bin.
Also, an online ff7 mod would be very prone to being shut down by Eidos. Of course, a from-scratch ff7 online game would also be prone to shut-downage.
So that's my constructive criticism. Lol. Sorry for being harsh.

I mean well, I really do. You just must be one hell of a programmer, and better than other game modders (especially those who created the GTA online mods, which are still unstable after 5 years).

Best of luck.