To the OP, why not look at dedicated video cameras. They do autofocus far better than any u4/3 system and can easily do wide angle and macro on the same dive. Still $3K is pretty low budget but you might get it done.
I had been considering this option myself. Over the past year, I have seen a few Gates / AX-100 combos with multiple ports on the resale market in the USD2,500 range. That said, I would still favour a used GH4 for the superior image quality, excellent MWB and ability to re-use lenses in a future upgrade. The GH4 is also a much more versatile rig for above the water.