There’ve been a couple of folks who have installed more powerful spindles, but haven’t had marked improvements in performance (or if there were, they haven’t shared that or I missed it or misunderstood). ( Nomad spindle motor....upgrade?
and Nomad 500 Watt Spindle Upgrade for the curious).
One thing which I’ve been wondering is if a different pulley arrangement might be advantageous — but I really suspect that having a more powerful spindle would then result in the need for a more rigid structure, and before you know it, you’d end up with a machine which would need to be delivered on a pallet, and would require multiple pieces and assembly onto a special-purpose table — ref. “The Wonderful One-Hoss Shay” and all that.