Yeah, that 80v-225v range is going to make things difficult.
I'm not an expert in SMPS, i've only made about a dozen or so and usually pretty shotty but here's my two cents.
To get the universal input and the isolation you could try first putting a boost regulator to push the voltage up to say 240v or more. Chips for handling boost topology are easy to come by. Use the 240v and send it through a full-bridge or half-bridge isolated buck regulator. Because the 240v is already regulated you'll get smoother output at the 12v end. Although you'll have to synchronize them to get best results.
Since the 240v is a design specification, you can tune your transformer to be perfectly suited for 240v : 12v operation.
Spikes are mitigated by the boost inductor and storage capacitor, giving your OVP circuit more microseconds to respond.
if you want a single circuit rather than the two independent circuits above, you can try a SEPIC converter or CUK converter, you can make them isolated. I personally haven't done anything like this so i don't know if it can handle the current.
Alternatively, if you like messing with transformers (I sure don't) you can drive the full/half-bridge circuit directly with the battery back and simply alter the transformer tap to suit the voltage range. It's still isolated. and you only need one control circuit.
As for optocouplers, they'll work but you got the problem of transient response. I've heard optocoupers just aren't fast enough to give you the extreme noise mitigation you demand, although i could be wrong on that point.
what i've seen done is the control circuit is actually placed on the secondary side and samples the voltage directly, the gate drive signals are transferred to the primary side by a gate drive transformer. Responds much faster than optocouplers, and doesn't exhibit aging that optocouplers do. The drawback of placing the control circuit on the secondary side is that you need an auxilary supply to start up the control circuit. But the auxiliary supply can be MUCH smaller, simpler and not as well regulated as the main supply.
oh well, my two cents. i'm probably wrong but i hope i atleast point ya in the right direction.
P.S. To get really smooth, highly efficient supplies, you can try looking into ZVS or ZCS tolopogies. Really tough to build but are the latest thing in SMPS design.