I’ll echo what’s been said above. A handful of supporters peering over the fence is one thing, but when it starts being shown on various media outlets it’s only going to give more of them the confidence to drive down and watch the game from over the open end. I doubt there would be any trouble with any fans other than Swindon nor thousands in number, but a few hundred of one of the better supported sides like Portsmouth or Ipswich would be a very poor look. We do not want this becoming an unwelcome headline either for COVID19 concerns or violence linked with football.
It needs a solution. Policing it is the obvious one but maybe marking off a few rows of parking spaces behind the goal as a no-go area too. The further back you are, the less you’ll be able to see acting as a deterrent anyway even if you are stood on a transit van. There should still be plenty of parking for match day officials, press, visitors to the cinema etc.