What is the best solution to make it portable?
1. To register a program's use of document folders and registry and make a batch, that before launch setup symbolic links and registry additions, so it can be installed on portable device together with its documents
2. Or to use sandboxie portable or not, and install program in a sandbox on portable
The best choice is to see if the PA.c launcher can handle the file, folder, and registry locations first by looking at the launcher reference. The second best option is to use the batch file that you mentioned, but I don't think that's necessary if you use the launcher right.
As for Sandboxie, I'd stay away from using that, Cameyo, or Thinstall because they can ride on dubious legal ground if you plan on releasing it to this community. Hope this helps.
If a program becomes portable just by installing it in a sandbox folder, it does seem a bit easier ...
I'll rephrase my answer then. If you plan on releasing the app to the community, don't use the easiest solution because it can hover on the wrong side of legal. If you are just doing it for yourself, go ahead and use sandboxie, cameyo, or thinstall. I kind of blatantly assumed that you'd want to release it for others too.
cameyo.com, that sounds even easier, I will try that one.