Sixgunnin,
Nickel is harder than brass and flakes off easily if bent hard, as forming into rifling would do. You could then get nickel flakes embedded in the forcing cone and bore, as happens to reloading dies. And there is another problem. Nickel-on-nickel (nickel-plated bullets and cases combined) will have a higher coefficient of friction than copper on nickel does, so you might shave nickel during bullet seating and your load pressures may go up.
As to plating and the rest, I would avoid that because of the potential for galvanic corrosion bonding. Back in the 1920's, Townsend Whelen thought it would be a good idea to tin plate bullets to reduce copper fouling. It did, but apparently he did all his testing with freshly loaded rounds. When they ran that combination for National Match ammunition, by the time it got to Camp Perry a few months later, it had bonded severely and to the extent some case necks broke off in firing and some bullets were recovered from the pit berms with their necks still attached and engraved by rifling. The pressure must have challenged proof loads pretty well. Needless to say, accuracy would not have been great with that kind of irregular round.
Tin may be a special worst case, but I would hesitate to plate anything on bullets without going through some systematic pressure testing, repeated as the loads age to watch for signs of trouble. Winchester uses something, but I don't know what it is. Maybe they would tell you if you ask. The do make
a .45 Colt load with this bullet type. Just don't confuse their handgun Silver Tip bullets with the Ballistic Silver Tip Combined Technology designs they have with Nosler. Those are more the color of a moly-coated bullet, though they are Lubalox, instead.