Nothing wrong with bringing it up if you didn't know the answer, although for future occasions the search function migh be a faster way to get a solution if there is one
Having re-read your question I now see that you actually asked how to switch between different GAME versions, and to that there's no easy solution in SH4. You could do that too with JSGME, but you'd have to create your own mod that switches the files that are different between the two versions. With the latest versions of IL2 that's easy because only two files need to be swapped, but with SH4 you'd be talking about tens or hundreds of them.
There's little need for version switching mod-wise, because the most up-to-date mods will be for 1.5. Unlike in IL2 it is not a beta patch but a finalized product, and it's unlikely that any new patches are released in the near future.