Please note that while on some wikisources it is the convention to remove the linebreaks inside a paragraph, on others — for example the Scandinavian ones — it is the convention that they should be kept (except of course in the rare cases that cause formatting issues). The point is that when you are proofreading/validating the text, you have to compare the wikitext and the image word for word and line for line, and without intact linebreaks you will easily loose your place in the text many times over. In my opinion, it is much faster to work on a text with the original linebreaks that make the wikitext and image match line for line, and I would consider it a rather annoying bug if they were automatically removed. So if you do go down this road, please consider if it should done using some kind of opt-in mechanism.

I am probably only stating the obvious, but license templates are supposed to contain machine-readable classes as defined on https://commons.wikimedia.org/wiki/Commons:Machine-readable_data since about a decade ago. Several wikis have implemented that in a half-hearted way or not at all, but I don't think it is unreasonable to ask folks to work on that, also considering that it should be less work than for example adding a copyright status to the wikidata pages of all pages.