You don't need to remove the starter just to not use it. If you do, there you need a plug machined to block the orifice into the cases. If you want, simply remove the wiring to the solenoid and change your handlebar switches.
You don't indicate where you want to relocate your electronics to, so there's no way to list what you need. Changing to a modern reg/rec usually provides an opportunity for some clean up and simplification of the stock harness. You're better off re-using the stock harness and "extend" the wiring to a new location. Then a later owner can track what you've done to troubleshoot.
If you want to be super clean, super simple, and flexible with oyur electronics, spend some dough on a MotoGadget m-unit, m-button and m-lock. Eliminates the key switch (RFID), eliminates the main harness altogether, and eliminates the relays needed on your bike. The m-unit is smaller than a pack of cigarettes, has all your fueses, relays, and circuitry. The m-button installs at handlebars, every control wire solders to it, then a single wire plugs into the m-unit. The m-button is half the size of your thumb and neatly installs in the headlight bucket behind the lamp. The m-lock is a fob reader for keyless ignition. Step up and do it right and save the modifications to the stock harness.
Time to complete? Depends entirely upon your skill level. MotoGadget install, 8 hours if you have all the wiring, connectors, and sheathing ahead of time.