Hi John and thank you for the answer,
1. I agree of course, but as you know not all members are aware of this especially new members who have to first get familiar with and learn so many things about Wikitree it might take a while before they notice this one.
2. I have no idea how large the overlap would be exactly of course, but working a lot on these projects I do know that some immigrants / emigrants and other profiles were from very well known families, maybe even some Royals, Aristocrats, Nobility or Gentry. But for most of them (the after 1500 until now ones) we can find church records and /or charters or (notarial) deeds, letters where the correct names, so the names they used themselves during their lives and names they were born baptized with, are mentioned , and pretty consistent, so there's no real big problem (no headache ;) ) to use their convention instead of ours for these profiles. Which for many Pre-1500 profiles of course is a different story.
3. Looking at the Welsh naming guidelines it seems this also is more according the use their instead of ours convention ? So maybe for the Euroaristo profiles (see the answer above) if the list with Royal Houses/ names is presented to make sure these will be used by members of the project for profiles part of these families (to stay consistent), but that it is made (more) clear that for other new and /or later profiles it is ok and maybe even preferred to use their convention instead of ours (if there are good sources showing people used the names with prefixes of course) .
Indeed naming standards have changed, that's also why we now have the use their conventions instead of ours guideline , and I'm glad to hear your not against this idea , indeed this change probably needs to be published more, but should be more clear or explained at the project pages as well, the British Isles are a bit more clear already, but maybe the importance of the use their convention instead of ours could be added or explained there as well for the After-1500 until now group ?
Maybe all projects for this group of After-1500 until now profiles could or should add something about this guideline at the project pages to make sure all members visiting those pages will immediately get a clear picture and are aware of this guideline ?
Of course this is the main reason why I started this G2G , it's important we all are consistent and very clear about what guidelines/ naming conventions Wikitree members should use for this immense group of profiles.