Regarding feet position. I'm assuming that >90% of current jet a/c have an RTO function on autobrakes. Thus, in an RTO, should they work as advertised, your feet are for steering and not stopping. Should, OMG, the RTO function not work, it is sensed PDQ by the alert pilot, and in the flash of a big toe nail your feet should be able to transition from heels down to heels up.
There will always be the argument in the case of a Stop limiting runway that any delay could be critical: but then you'd have to have a multiple failure of the system that caused you to RTO and an autobrake failure. Statistically unlikely.
The same argument can go for landing. Where do you put your feet then?
In my sim experience I see too many crews disarm RTO autobrake function during an RTO. That is less likely to happen heels down. In a strong x-wind slippery runway I would rather have my feet concentrating on steering that stopping. If you inadvertently disarm the autobrakes you now have a greater problem with pedal steering & stopping.