Yep. Several people have recreated MessagEase inside of Multiling O Keyboard. With extra functionality.

Edit: you can check out the 50 some odd page manual HERE

Macros: What MessagEase calls Macros, Multiling O calls Auto Text. It has a separate plugin for managing that. Type in the brief and the replacement will show up in the suggestion bar. Entire words or sets of keystrokes can also be bound to keys. Then there is clipboard manager that holds up to 16 items. And options for auto-time/date and order of auto-punctuation when multi-spacing.

Unicode in Multiling O: From the manual - Any Unicode character can be entered by typing «u» followed by its hex value. There is a shortcut for this in the suggestion bar. Pull down on suggestion bar and select [U+...]. Or you can create Unicode Keys on your DIY layouts using button code [U+xxxx], where xxxx is the hex value. (Which you could put inside a multidirection button, on a different layer)

Compose tables: I'm not sure what you mean. Are you talking accent and diacritics? Multiling O has AltGr. I type E, I bring up the default AltGr menu and I've got options for 14 kinds of E with dots, curves and accents above and below them. Multiling O also supports long press keys in DIY layouts, deadkeys, and something called "key modifying rules" that I haven't figured out. Maybe a hardware keyboard thing?

Multilanguage/Script support. Multiling O supports over 200 languages through plugins. The layouts are considered separate from languages, and they can all be swapped on the fly through the gear menu. So if you want to try typing French with a Cyrillic keyboard, feel free. Or Predictive T9 for English and maybe a KalQ variant for Spanish. I don't think the Klingon language plugin is going to be any help for anything other than geek cred, but knock yourself out.

Ctrl Character: Again, not sure what you mean here. If you are talking hardware keyboard like Ctrl key, then yes. Multiling O has the basic ANSI/ISO keyboard keys that by default can be accessed through the FN layer. Ctrl, Alt, Esc, ScrLck, NumLck, Insert, F1-F12, etc. Also a handy System Info button. Ctrl+Z/X/C/V/Y all work as expected in iA Writer. Commandline wise, in Termux Ctrl+C/H/D all seem to work. On the other hand, there is a dedicated ^C button on the FN layer as well, so there might be some trickery going on...

Emoji: Yes, it does emoji. No stickers or Gifs though.

Anything else? As stated before, you also get split, floating and/or transparent keyboard options (to maximize screen realestate), remapping of attached bluetooth keyboards to match equipped softkeyboard layout, next word prediction, and the most comprehensive set of options for swipe typing I've ever seen in one app (though NIN 69 comes close). This is all without being bound to the developer's included layouts. So you get pretty close to the layout you want AND most of the features you want. Unless you want chording. (Trust me, you don't want chording.)

Though in the end, unless you use a custom layout (like Tarmak) on your home PC, you'll probably find it doesn't improve your user experience that much over just using Qwerty on Gboard. Turns out muscle memory is still a thing, even with different muscles.

Edit: Other things I forgot.
   Special Key customization. The settings menu has a separate subsection for the behavior of Space, Enter, Delete and Gear Key (plus another whole submenu for physical keyboard keys). Of particular interest, swiping the Spacebar brings up the Language Menu by default, but this can be swapped out for moving the cursor, as Gboard does. Language menu is then brought up by Spacebar long-press.

   Gestures. Multiling O Keyboard doesn't only support Swipe typing, but also Fleksy-esque 4 direction Gesture shortcuts. Single Touch Slide and Slide+Hold only work with swipe typing off (and off of non directional keys), but the Multitouch Slide shortcuts are free game.

   Programmable Suggestion bar. This setting is found under the 'Word Prediction' submenu. Basically a Macro menu for frequently used items. Cut/Copy/Paste, Insert Date/Time, paired punctuation, emoji, the unicode thing, etc. The Suggestion bar itself can hold several pages of items. Just pull down to the Lock key (lower left), then use the arrows to the right and left of the Space Bar to navigate.

   It is tiny. The keyboard download is less than 1Mb in size. Granted, that is without plugins. Even then, it is practically nothing compared to the big name keyboards.

Unfortunately, I don't have any speed data. Considering how flexible the keyboard is, I'm not really sure how it would be measured either. I mean, I guess if you are not using completions, corrections or predictions then you could just make a copy of Fleksy layout and call it the World Record holding fastest keyboard?

Speaking of completions and predictions, did I mention MOK has a 'Vowels Optional' and 'Guess Missing Letters' word completion settings? Both in beta, but available under the Word Prediction submenu. Sorta like a built in shorthand system. (I discovered this as someone posted a vowelless keyboard idea somewhere. Haven't played with it.)

Looking at the 'Key Chord' article, by Compose you mean Deadkeys and Stickykeys, right? I think that is more or less how MOK handles modifiers already. I was having trouble figuring out how diacritics worked, but it turns out MOK uses the unicode Combining Diacritical Marks for Deadkeys. NOT the standard symbols. The combining marks are on the AltGr layer and the standard symbols on Symbols layer, which got me a bit mixed up. Knowing that it would be fairly easy to add those to your layout. Maybe a dedicated 9 way button?

Likewise, the example Key Modifying Rules mostly use the combining marks. You can create your own rules if you want to use the regular symbols, or do something completely different. By default : followed by . gets you a blobby smiley... thing. (Note: diacritic deadkeys have a setting that can be quickly swapped to either ~+n=ñ or n+~=ñ, but Key Modifying Rules need to be changed manually. Or you could create Auto-Text macros, but then you would need to turn off 'Insert Space (after picking)' in the Automatic menu).

One More Thing: When using a deadkey the keyboard glyphs will change to display the character to be typed. Like on most keyboards where you hit shift and the keyboard shows capital letters. This makes the character-diacritic order somewhat easier than the reverse.

While I am talking mechanics anyways, I should clarify that there are at least two types of long-press actions. There is 'long-press to access underlying symbols layer'(optional) where the two layers are automatically overlayed aligning at the upper left corner, and then there is 'key with defined long-press menu in the layout' which you have to do yourself.