My personal feeling is that for individual use and casual play for v-set pieces - go ahead! Absolutely no problem there. Make all you want (really nobody could stop you anyway)
But as far as tournaments - there are some who might cry foul. Officially it has to have the base of the figure it is representing (a legit base). Of course - as for the V-Set, since there are no actual figures for these pieces, this is gray area.
For competitive tournaments I would worry about using molded reproduction pieces of non v-set figures.
But V-set pieces is another story.
My good friend is also molding custom figures. He is only doing them of V-Set pieces, since they don't exist he's making them from random existing figures (SWM, D7D, Hero Clicks), then making a cast mold for the finished product. I personally don't find any fault with it for the V-Sets, but I'd be curious to see how a judge ruled using them in a tournament.
To me - it's always been about playing the game. I never have blinked when someone wants to use a proxy figure (not the unique droid, just any substitute
). I'd rather someone play an optimal squad than play with less than that because they can't afford a figure.