I have no idea whether this concept is feasible at scale, but it seems like the best way to know is to work on developing the concept. If we don't try, we'll never know.
No, it's not feasible. The best way to know is to do math. You can work out exactly how much electrical power it takes to melt snow/ice per unit area, then multiply that by the total surface area of a freeway. It's a lot of power, way more than the panels themselves can generate.
Fortran (the 1977 standard, not earlier versions) was/is a decent language.
That pretty much invalidates whatever point the rest of your post may have had.
The proxy fetches the content from the remote server to a local directory
If a free program wanted to do this, it would be readily visible and available for inspection to determine what exactly it's doing.
That's the fantasy world that free software proponents* like to trot out. While it's technically correct, in the real world, however, very few people have the ability, motivation, or time to code-review every application they use.
* Not that it should change my point one whit, but I also am a free software proponent, but not for that dubious reason.
For example, if I follow Bob, then I (and everyone else who follows Bob) would receive Bob's tweets. If EvilJerk also follows Bob, he can be as outraged and tweet about it as much as he wants -- nobody except those who opted-in to follow EvilJerk would get his tweets.