Some more food for thought…I’ve installed this plugin on three sites.
About the styling–I discovered that on the first two sites I had checked the box to generate a mobile sitemap without reading the text next to that. With that box checked, I got the unstyled document tree. On the third site, I read the text and saw that it would check to see if the plugin is installed on a mobile-only site. I thought it would just check that condition and do something for mobile sites, but I didn’t think it would shut off styling for non-mobile sites. I left that unchecked and got a more styled file as seen in https://accessible-techcomm.org/sitemap.xml.
I went back to the first two sites and unchecked the box to generate a mobile sitemap. (I also modified the .xsl file to my liking and that worked.)
The sitemap.xml file generated for the first two sites includes full links (using your xsl file and also using my version). See https://blog.baeecorp.org/sitemap.xml
But in the third site the domain part of the links is not included–only on the first link. Google Webmaster Tools doesn’t recognize these as valid links and gave me 350 errors it said I should fix. See
https://accessible-techcomm.org/sitemap.xml. Do you have any idea why this sitemap doesn’t include the domain?
(I don’t think the theme would be the cause of this but the first two sites are using the Photocrati theme. My third site is using a Blaskan Child theme.)