I actually don't anticipate long periods anywhere near the full load of 90A, the motors themselves are only rated to 66A anyhow, this is basically flat out. Re the ESC issues I agree this is pretty new territory, got to learn some place, somebody needs to be first I guess. The ESC's are easily changed out anyhow.
To make the picture a little clearer this 'plan' is going into a 1.6 metre long model of a 'super yacht' (Moonraker) that has three brushless motors (XK3674-1650KV), these are each driving a water jet (KMB Jet28). So three batteries, three motors, three jets - theoretically that's 3kW on full load but the ESC's and motors are water cooled. I'm estimating a run time in excess of 30 minutes.
The jets however have pretty tight tolerances so they aren't going to swallow cigarette ends / feathers etc happily, I want to not only protect the jets but also the motors / ESC's although these are easily replaced - the jets not so easy as they are in integral part of the hull.
This is a little off topic I guess but I'm using an ATMega2560 in a similar manner to the 'Pixhawk' used for drones although I'm not planning any autonomous operation.
The ATMega2560 will operate all motors, servos and also pitch controls (ultimately via a 9 axis gyro) all via an FrSKY X8R coded for 16 channels communicating using SBUS and a Taranis X9D transmitter, I also have a Ublox Neo7M GPS and compass installed. I have an additional 7 channels needed for LED / lighting control but I plan to build a touch screen WiFi controller to handle this. The model control is pretty complex but that's a whole other thread.