The real world problems with bringing up the issue of legal private machinegun ownership are many. First, is the public perception of machineguns as things only govt agents, the military, and lawbreakers have. And with over 70 years of brainwashing by the entertainment media that's not going to change.
Second, bringing the issue into the public eye in today's "safety concious" social environment is horribly risky. Many folks are working hard to rid us of the scourge of SEMI automatic weapons, think how popular the idea of FULL Automatic would be.
It is extremely doubtful that we could win any improvement in the current laws. Note that even in the Heller decision, the court did not say we have any right to full autos, using language about "in common usage" which full autos are assuredly not. The benefits do not come close to justifying the risks.
As for a revenue raising measure? Consider that the one tax the govt has never bothered to raise is the NFA tax. It was $200 in 1934, and is still $200 today. Would it gain us to see the registry reopened (the absolute best you could reasonably hope for) if they decided to raise the tax to say...$10,000?
Raising the NFA tax to $10K for each transfer would certainly be a revenue raising measure for the govt. And with the registry reopened, the price of NFA weapons would go down (because the supply was no longer fixed), but with a huge increase in the NFA tax, we would see no price break for the buyers, rather an increase, effectively pricing them out of reach of everyone who isn't tremendously wealthy. And it would pass constitutional muster, in the sense that the law no longer "bans" a whole class of firearm. Making it hugely expensive isn't a legal "ban" even though it is a de facto practical one.
Yes, it would be nice to be able to return to the standards (and costs) of yesteryear, but it ain't gonna happen, even including everyone in the nation who ever wanted to own a machinegun, the numbers are just too small, and that "special interest group" will get absolutely no sympathy from the press, or the general public.
The most likely outcome of bringing up the issue is enhanced regulations and increased costs. Neither of which does any of us any good at all. Rather the opposite, in fact.