I think you're overdoing it! By adding everything on AltGr, you'll end up with many unintuitive placings like ćĆ on the comma key instead of on cC – or nj up on the number row! And I have no idea what happened to bring ⅞ into the mix...  ￣(=⌒ᆺ⌒=)￣

I think it's a lot better to do like I do: Make one variant for your main language, then add dead keys with everything that doesn't fit logically on the AltGr layer.

As you say yourself: Savetier-X is a compromise. In fact, it's a bunch of compromises because you try to do everything at once.

With standard Colemak or my Colemak-eD you could already write all the letters you mention. Certainly with Colemak-ed using the EPKL program!

Using EPKL to get a layout, you don't have to use any additional programs for tricks like the 'sch' mapping. In EPKL, you could get that with '→sch' on any mapping.

And I think you've hurt your layout by keeping WASD in place. That spoils the typing efficiency of Colemak, since the layout was meticulously designed to get good bigrams etc. If it had been possible to keep even S in place without spoiling the efficiency of Colemak, Shai would've done so. In fact, he did at first but then abandoned it.

Finally, your layout is unergonomical in not addressing the wrist angle for the left-hand lower row. Consider using an Angle mod to fix this problem.

Are those lj/nj/dz/dž digraph characters actually used in practice?  Unicode recommends against using them, they were only added for round-trip compatibility with legacy character encodings.

Although they form a single letter in several languages you mentioned, I think formally they should be written using two characters.
(Otherwise it screws byte-for-byte searching/string-matching in non-Unicode-aware applications.)

Edit: Slovene/Serbian/etc Latin keyboard layout doesn't have these digraph characters either.  (Only the Cyrillic counterparts љ/њ/ѕ/џ are actual single characters.)

A single letter is not the same as a single character though.  For example, until recently LL was a single letter in Spanish (largely corresponding to lj/љ btw), but there has never been a single character for it.  It requires two keystrokes.

In my language Dutch (Flemish), "ij" is sometimes considered a single letter as well (more so in the Nederlands than in Belgium), and forms one unit in vertical text like you mentioned.  But nobody uses the Unicode "ij" digraph character, even though it exists.

The Unicode digraphs are there only for historic compatibility reasons (Unicode wanted text converted from-and-back-into a legacy encoding to be identical to the original), and are not intended for use in new texts.

I know. That's exactly the point why I'd like to keep them there, may it be only for linguistic purposes and slavists.

Slovene, which uses a simplified Gaj's alphabet, doesn't use these digraphs at all. Gaj's latin alphabet is used for Serbo-Croatian (BCMS) and latinized Macedonian.

I get your point. But as there was still space for them, I see no reason to not have them on an "all-slavic" layout, the typer has still the freedom to choose whether to use d+ž or dž :-)

The thing is, I started out with a Colemak variant in principle very much like yours back in 2007–2008 or so! But since then I've changed my tack. Using dead keys I can have room for so much more glyphs and they can generally be in more intuitive places. Unless you want a layout only for yourself I believe that's the way to go. It's easy for me to remember where I put an accent dead key but it'd be harder to learn and remember where every accented letter for that accent is. Plus, with the dead keys I can also overload them: On the acute accent DK there are also superscript-related glyphs, and on the grave accent there are subscript-related glyphs etc! And I can link dead keys, for instance by combining the slash and maths dead keys I can turn the ≡ into a ≢.  ( のvの) c[_]

I uphold that one should use a variant suited for one's main language. For the times I write another language I find that Colemak-eD support them quite comfortably although I wouldn't want to write long passages that way. Hitting AltGr+' (for acute) or AltGr+; (for umlaut) is nearly as comfortable to me as hitting AltGr alone. One thing that helps comfort is that you can let go of AltGr before hitting the letter you want. To type capitalized letters it's certainly more comfy than full-chording, especially when combined with a sticky Shift modifier. I'd imagine that typing, say, Ș/Ț gets a bit stretchy on your layout? For me, I have to stretch a little for AltGr+8 but then it's a matter of tapping Shift then s/t.

Yes, I know. There was a discussion about making the Angle mod a standard for ISO keyboards but it stranded. I'd still recommend it heartily! Keeping your left wrist straight while typing is a lot more comfy, and using the index finger for C is not good for the bigram stats. See the BigBag link in my signature if you're unsure what the ergo mods are.