I don't really wanted to use blood magic. :S The pack is being made for a specific server, and there are people who will not like it (i might sound one sided, but only because i'm one of them).
I known that Thaumcraft is no option.
I tried witchery because it at least looked liter, but we ruled it out because of security issues. It was too easy to destroy someone else and/or their belongings, and we're sure that there won't be any log (these types of events are never logged).
Botania was my bet, but i wanted to see other options, if theres anything better.
Botania is a no go, depending on how rubbish your computers are. Botania will have particals shooting everywhere, also large mana setups while not horrible can make a significant performance hit. That being said you do have to go goo goo gaa gah crazy with mana gen.
So you want a lightweight magic mod with no exploitable PvP mechanics? Try "Professor Weaksauce's Fake Panzy Magic Mod" ohh wait that doesn't exist.
Actually there was a mod that was in one of the older packs
"Arcane scrolls" it
"looked" kind of light weight but
I found it to be remarkably lame, at least compared to the big Magic mods. The mod essentially added limited use items that where created from your exp and I think some paper and some odd dust material, had things like fireballs to teleportation and other sort of useful stuff. Don't think it's being developed for 1.7.10 though, but it sounds weaksauce enough to fit your bill.
Also those suggesting Blood magic as a light weight magic mod must be joking with you. I mean it's not as huge as Thaumcraft or better yet ChromatiCraft (that thing is fucking BIIIIG) but it's not light weight, maybe middle weight.