The 'emphasis on non-English mappings', you say? This is not true. I've provided a couple of PKL layouts for standard English with or without ergo mods, all without any locale mappings. There are 'virtualkey' layouts for both ISO And ANSI keyboards, but if you want my own mappings (Colemak[eD]) that's provided for ISO keyboards only. I believe in ISO keyboards for Colemak[eD] as they allow the Angle mod. All the Tarmak and Mirrored layouts are provided only for standard English, by the way.

If you don't want to use the RAlt as an AltGr, you probably won't be able to use Colemak[eD] anyway unless you use something else as your lv3 modifier. I've yet to come across anyone who does that, although I've seen options in xkb that allow other lv3 choosers.

For Colemak[eD] on ANSI keyboards you'd have to change some VK_# mappings in the layout for the symbol keys. I'll consider adding an Colemak[eD]-ANSI layout too, but it's a bit of work to maintain many PKL layouts and it seems to me that ANSI users often don't want lv3 mappings anyway as indeed seems to be the case here?

The help images I've made have been ISO-based. I can make ANSI-based ones but it'd only be a cosmetic difference for all the extra work that'd entail. I'm sure everyone can wrap their heads around a different location for the \| key and ignore that extra <LSGT> key in the images?