Varying Voltage

In essence as long as the motor is less than our voltage limit, and between that and the current drawn it doesn't exceed 1kW (and doesn't overload the thermal cutout) then it's up to the teams to determine how they want to control things.

Here the suggestion is a max of 5A @ 16V, which is 80W, this leaves ~920W of power remaining for the stator supply.

In terms of how to do this? I see no reason why this couldn't be done while the motor is running, and something like the proposed module is probably the way to do that today.

However if the current draw is expected to be 5A I suggest this particular module is NOT suitable. In general I would choose a spec that gives some headroom, i.e. if you're going to draw 5A then an 8A or 10A controller would mean the unit won't running at its maximum capacity throughout. As a result I'd anticipate it less likely to fail through overload.

In addition to this I'd suggest that there are modules that also provide ajustable current limiting, and that this could be useful to them in some circumstances.