If you only need a user adjustable knob, I would consider an infinite switch:
https://en.wikipedia.org/wiki/Infinite_switch, mounted in an electrical box,
You will want to use nickel-plated Hi Temperature Wire Terminals and Crimp Connectors, and HI-temp fiberglass or silicone insulated wire rated to 250-500°C
Triac based light dimmer will do the job. It must be designed to stand 1500W incandescent light bulbs.
Constructing a safe one is far from trivial. A ready to assemble dimmer may be the easiest choice. "Rotary light dimmer 2000W for incandescent bulbs" is a generally available device. In advertisements there can stand SCR instead of triac.
TL;DR: Given that you took into account the efficiency $\eta$, and added on top of that the safety factor $N$, in most cases you will be selecting a motor capable of performing the task you describe.
Account for acceleration
You'd only need for acceleration and the mass moment of inertia, if you had significantly high values for acceleration.
For example, ...