So while 9x MPLas is tempting, I think that it would be outclassed by the 5SS in almost every way except for Alphas. As such, going with standard lasers seems to be a decent option as you can fit in quite a few due to the weight savings. Similar Alpha to the 9x MPLas, but with much better range, though worse burn time. LLas go in the right shoulder to take advantage of the highest hardpoints. This is a little hot, so 3x LLas + 5x MLas might be an acceptable alternate and you can squeeze in a STD280 and a bit more armor.
I don't see how you can use both the large and mediums at the same time. You can with small lasers though for a very impressive mixed short range volley that doesn't cripple you with heat. Triple LLAS is solid.
New tech update. Pretty sure that LE can make it a more viable build, can remove ERML from the arm and/or one from the LT for more DHS, freedom to remove arm armor and add a bigger TC. Still, I think this is one of the stronger IS laservom alphas out there.