I can readily understand why installers would go the micro inverter route. No solar cables, HVDC switches, fusing, HV DC wiring, HV safety, 400vdc on roofs for the fire dept to deal with.... etc etc.
But for off grid, it has no merit, only draw backs.
On grid needs no control, off grid requires control. On one of the outer islands here we have 40 panels in one area, and 20 panels hundreds of meters distant. The 40 panels run at low voltage via a 7kw 48v controller costs maybe 50 dollars to build, and is local to the battery storage.
The other 20 panels are AC coupled via a big GTI back up to the house, and helps run the shearing shed and Reverse Osmosis water plant... no control required, as it runs in deficit to the RO and shed use. Micro inverters would just add huge expense, and no gains, whereas second hand 5kw GTI's are cheap, and if you want, you can configure them to accept generator HVDC and still charge the batteries hundreds of meters distant.
So every installation has it's own foibles, and micro inverters just do not fit in any off grid circumstance I can think of. Offer no advantages, only problems once you leave the on grid environment, as they offer very little if any benefit, only challenges as you have found.
Anyway, thats not the issue here. You have micro's installed, thats what we have to deal with.
We can do things once we centralize the power, by then we find control too hard to do at the panel end sensibly, so we are left with AC dumping, cheap, simple, easy to do..... so we might as well do it.
I would just build a nano controller, with 3 stage charge control, and couple that to a water pre heater, and perhaps an array of oven elements in case the water gets out of hand.
That way your field wiring is simple AC to the panels micro's... thats it. Your control wiring is all local..your back in control.
My conditions are very remote, and I could never use gear that required outside help/interference... does not compute.
Starting heavy loads is really not related to the transformer, but to the low impedance storage you have available. If they sprung for some serious capacitance in the HF units, they could start stuff up just as well as the transformer designs. Mine can easy do 20kw surges for 5hp induction motors, as we have the battery as the storage at 48v, but we could just as easily have a 350v battery of only a few AH instead of the HV caps, in the HF unit, and see the same result. The transformer is only an impedance matching device after all.
..........oztules