First of all I've got to say that this is a really great mod that gave (and gives) me lot of fun, as the vanilla units really are a joke.
After having said that I'd like to make some suggestions:
Mercenaries
Do you plan to create a function to hire mercenaries, Swiss Halberdier? That is probably a feature for the future as I can't believe that it would be easy to mod, but your Swiss units for example would make perfect mercenaries.
Regional units (existing)
Empire: Total War has quite a lot regional units as I would call them: units that can be recruited if a certain region (or sometimes several) has been conquered. If such a region is conquered some nations may use the units, while others may not. It would be awesome if you could make those units available for all factions or for those which have a realistic way to recruit those units.
Examples:
- Uhlans (I believe) in Preßburg for Prussian conquering forces.
- Sikh-Infantry in Punjab for Mararatha conquering forces. In the 19th century the britihs for example had several Sikh regiments, so the British at least should be able to recruit them.
- Some hooded skirmishing guys (I forgot the name - something like Pendulen) in the area of Austria
- Cossack infantry and cavalry in Russia. I believe they might or would have fought for other nations, most likely Poland etc. as the Cossacks had trouble with Russia from time to time and were not the most Russian-loving I'd think.
Regional units (not yet existing)
It would also be awesome if you could add additional regional units, like for example the Connaught Rangers as a line infantry regiment with slightly better stats than normal line infantry. They would only be recruitable in Ireland.
Elites needed!
There are several factions and/or regions that need elites in my eyes. For example the colonies in Africa and India as well as in America do not have any Elite units (except maybe Guard Infantry). Moreover Native units that can be recruited in e.g. Colombia by the British shouldn't be the same kind of units as those recruitable in Alaska or Canada. Even if both units are of Native origin, they would differ in appearance and behaviour I believe (cf. the Maya and Apache units from Medieval 2: Total War: Kingdoms where the North and South American units did look and fight differently).
Also Russia needs some Elites - maybe some Asian mercenaries similar to the Swiss ones (don't know if that would be historically accurate).
Reskins and Highlanders
I really like the Highland Infantry you enabled me to play with! But what I don't like about those Highlanders (including the Royal Eccossais and the Black Watch) is how they look. I don't think the Highlander uniforms do the units justice. If you do reskinning as well as creating those awesome new units that would be something that needs a bit polishing I think. Regarding the Highlanders I think that you maybe could add another Highlander Infantry: one that's only slightly better than Line Infantry in regards to shooting but has superior morale and melee stats. Just as a thought.
Other Mods and units
I've seen that you have a version of you're mod for "A Proper Empire". I played that mod some time ago and liked the "Preußische Riesengarde" and "Van Ziehten Husaren". Could they maybe be implemented in this mod as well? Also I remember someone adding firearms to the Pirate mobs and the Russian Srteltsy (different persons, I don't remember where I found it, though). Those might be interesting additions to you're mod, too.
If you don't want to use any of those ideas, that doesn't matter (much ). I myself can't mod, so I'am more than happy someone takes care of the colorless units of vanilla ETW and hope that you consider some of my ideas.