You are very wrong about my locale proposal! You were looking at the "Keep local symbols" variant, which some require. I quite strongly recommend the "Unified symbols" layout. Furthermore, it's harmonized for Belgium/France/Canada so it could be useful for many!

I know, it's a lot of text and you're tempted to skip directly to the nice images. ;-)

   
    Belgian+Canadian(Intl)+French 'Unified Symbols' Colemak[eD]

As you can see, my tack is to put the accent dead keys directly on layer 1 – the ¨^ one where the locals are already used to it, and the more important grave one right next to it! – apart from the very common Éé which deserves its own key. I'd also recommend using CurlAngleWide with it, to bring special keys to the middle and the very rare K to the middle trench.

In my Belgian/FrenchCanadian Colemak[eD] variant, letters like Œœ and Çç have to be accessed with the AltGr key but I think that's quite acceptable given their frequencies and the relatively easy access (in my opinion).

I don't remember Endaka's French Colemak all that well, but I think that my locale variant may just be better all in all. It has more advanced functionality, and to me it fits the bill.

Bépo seems nice to me, although of course I'd prefer a localized Colemak since that'd really turn the Colemak wheels faster! Also, my locale Colemak is easily transferrable to another language while this is very specifically geared towards French typing. Some French will like it for precisely that reason I guess, but it won't change anything for the rest of us as it'll be an isolated phenomenon in all likelihood; much like the Russian or Israeli layouts (but more ergonomic at least).

You'll need an ISO keyboard to type anything locale, pretty much. The ANSI keyboards have too few keys, sadly. One big advantage you get with that is that you can more easily use the Angle mod! :-)

An interesting feature is how Bépo almost has a Wide ergo mod built in! The very rare K and some punctuation gets moved into the middle. They don't seem to encourage a wide hand position with it though, so maybe it's just a freak coincidence. Without a wide position it seems silly?

Another nice thing with Bépo is its huge dead key lists. I've looked to them in my PKL files because they are so comprehensive (but then I added more, of course...!).

Also, the layout jungle will only get worse if each country starts inventing their own language-specific layout.  Eg. if Italy would consider their own layout as well, it will not be Bépo based, given how specifically Bépo was designed for French.  Whereas one "pan-Roman language" layout with local variants (Colemak, of course) will probably give each of them 98% of the benefits, cost less in terms of standardization, and will be much easier for international users.

On the other hand, the more different "official" layouts are available, the more the world will "accept" using different layouts (eg. at workplaces), and the more people can and will actually think about which is best for them individually?

The ten most common letters in French are, in order, esaitnruol.  Q and u (and digraph "qu") are much more frequent than in English (with "ue" a common same-finger digraph), and h, w, g, y, f and b much less frequent.

Besides é (1,5%), other accented letters à, è, ê, ç, û, ... and digraph œ have a lower frequency combined than é alone, so indeed only é would really require its own (102nd?) key, without (re)moving a lot of other symbols for more accented letters like Bépo.

I don't think there are other trivial improvements.  The least-impacting change would be swapping H and L, as they are on the same finger (unless you consider Colemak L to be a better position than H of course).  U should perhaps move as well, but there's no obvious position it could take.  I thought about swapping it with W to make "qu" a roll, but it's not a very nice one, and makes for a very bad "qua" trigram (and a way too royal position for marginally used W).  So significant improvements would have to come from multiple key switches, which usually come with increased cost/benefit ratios compared to the standard Colemak layout.

Are there any native French users on this forum who have compared Colemak with Bépo?