Several issues:
I think the MVPA might want to deal with issues like this, but are simply unable. I know when all the Demil B & Q stuff got pulled a couple years ago, I spoke with several Officers in the MVPA and they told me they had a lobbyist and an attorney. They probably don't have these just to keep doing parades.
I think the issue with them is that they are too busy running around like chickens with their heads cut off because the hobby is changing and they don't know what to do. This is common in all kinds of car clubs right now. Traditionally, people joined clubs to meet other people with the same hobbies, be they old cars or gardening. They paid a membership fee, got a newsletter, some discounts and the club had a little budget it could use for whatever. But with the advent of internet forums, traditional clubs are losing membership and fast. This isn't just HMV clubs, but all kinds of car clubs. What's the point in paying $25-50 a year to get a newsletter once a month with some free classifieds when a giant forum like SS is available 24/7?
I don't think the MVPA has figured out how to deal with this. Because as their membership declines, they have to deal with smaller and smaller budgets to make things happen.
On to the bigger issue:
1. For a unified voice, that means everyone has to more or less agree what they are, what they want and what they can reasonably expect to obtain. This means compromise and most people just aren't willing to. Anything less than 100% pure version of their goal is worthless.
2. Infrastructure - there would have to be a group, run by people with time on their hands, who could manage lobbying/legislative issues in multiple states at all times. That's tough-most of us have jobs.
3. Revenue - the sheer fact of the matter is that at both the local, state and federal level, money talks. If we as a hobby can not find a way to come up with sufficient funds to put up effective lobbyists who can counter the message that opposition groups are putting out, we're dead in the water. Not only lobbyists but PR campaigns, public engagement, etc.
4. I know this is going to be unpopular, but this hobby needs to clean up it's image. We need to present the image of collectors of American history, protectors of historical items of note. Not tin foil hat wearing kooks waiting for the world to collapse. I am sorry if that rubs some of you the wrong way, but it's the truth.
Ultimately, how could a unified voice be created and managed, realizing those truths?
You have 2 choices: Force, cajole or persuade the MVPA to get it's act together. The MVPA needs younger Officers who understand the paradigm shift to the hobby due to the internet. Find a way to make the MVPA's membership fees worth it to young people who are currently getting their hobby interaction for free through SS, G503, etc. Grow the MVPA. Get to 20K or 30K members. Use that increase in revenue to pursue the goals we talked about (attorneys, lobbyists, PR campaigns, etc.). Convince the MVPA to join forces with other groups like the ATHS, SEMA, etc. The hobby is too small on it's own to make a dent in politics, we need help.
If that won't work, you have a much harder task.
You (or someone) will have to create a group, find a way to get 10-30K members, raise money and do everything I just said on their own.