We know they don't want you to have them, but if the government could earn more from the vehicle or armor from a private sale (like they do in the UK), then why sell it as scrap? Is the US government so wealthy they don't need any extra change? A scrapped APC is probably worth $5k, but in de-milled driving condition, its probably worth tens of thousands......
The best way is to apply public pressure on the Lawmakers to change the rules. Research the movement to reverse the required scrapping of used brass (once shot brass). Public outrage made them reverse the rule and you can now buy it from GL again without being forced to mutilate it. (if you have a 53k lb capacity trailer.
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It can be done, but it requires that people organize and present a unified voice of their concerns to their Representative and/or Senater.
I would think the lose of history would be the biggest leverage. In a time when museums can't afford to preserve these vehicles, there are private collectors that are willing to spend time and money to preserve these historic vehicles for future generations. Point out that these vehicles are displayed and that the public has access at air shows and other events, unlike other collectibles which are locked away and never seen again.
This could be done, but it requires people voicing their concerns and getting a small percentage of the public to agree and call their lawmakers. (I write mine several times a year, it does effect their voting, but only if they see more then one of their voters being concerned.