i played arround a little with granades on the TC, they are a lot of fun. however people say they don't do that much damage in endgame. however I'm planning to build one on live servers but I don't have enough time right now.
anyway, i guess you could work with massive +skill weapons. e.g. if you skill your mm like this:
http://hellgate.ingame.de/charplanner/marksman/?l=50&aa=0&a=00000000&s=0040a0010040a01000400010a40 and get 2 one hand weapons with +3 on each of the granade skills (ultra rare I guess) and 2 one hand weapons with + on the strike skills. maybe a +1 a skill helmet may help too. this way you would be using a granade weapon slot, a strike weapon slot and an additional slot for ... hum dunno lee's with ignite i guess or dual hue's.