You might have a problem. Even with a couple of people, with all the mods in FTB, you have a lot of data to send. I had a tekkit server a while ago, on my laptop to test some stuff. I had two players, and they both had issues when they got near my base, sometimes the world wouldn't load, and sometimes they would just straight up crash. I haven't measured the amount of data it sends to each player, but it is certainly more than vanilla minecraft. I cant really say what upload speed you would need, but don't be surprised if you get slow world loading near some complex machinery and whatnot. I would recommend setting a limit on timers, as those things cause so many block updates, its hard to keep up.