As a fan of the warmage from 3.5 compete arcane I can offer a few ideas.
1.Wand combat: this could fit into various niches in the magus setup. one way is to have wands work with spell combat. This could be improved by a magus arcana that lets you stab the guy you are fighting with the wand like the wandstrike feat from compete arcane.
2.As a lot of the Magus arcana are one shots each it means that long battles will sap a magus' only advantages quickly. Inset have some of them be determined by our int modifier.
3.Casting on the fly. A magus should be a master of combat and be ready for any situation, but if the adventure takes him under water well using that burning hands he prepared just went out the door.Being able to cast a spell that fits the situation should be the hallmark of this class.
4.No need for heavy armor. I know having an option to have heavy armor seems like a good idea but if a guy is still alive at 13 using nothing but light and medium it means he has a good dex or his DM has bad rolls. Ether way changing armor 2 times can be quite a waste of gold. There could be a lot of other things that could be given at this level.
5.Cleaving spell strike. This is just an idea that I hand that may or may not be a broken. The way it works is if you kill a guy while using spell strike you can hit another guy in range with the same bonus/spell.