Chainfiring the ER lasers on your 4P would be effective but you might run into some heat issues up close. You could drop down to 3 ER large and then run 4 mediums with an extra heat sink with the same tonnage. Also adding endo-steel will buy you some tons for leg armor and arm armor.
The 4H looks good but will benefit greatly when you can get double heat sinks on there.
What's your player name on MWO? We've got a fairly large group from SimHQ on my friends list, I'll add you if you want.