This thread is almost a wish list ...
I like the multiple inventions for Naval. Would like similar for Army... and more for Naval. (German WWI optics and shaft design was superior to British ... just ask the crew of HMS Queen Mary).
And, no, not a mod ... no VIP, no mod, no 'cheat' ... I mean, I can always mod and cheat to my hearts content. Would be nice if the official game had all that mod stuff in it. (It will be interesting to see HoI 2).
Still, VIC is a fine, if inconsistent, game.
Finally, double the number of resource types and more factory types! (Ok, that WAS a wish).
To fix some non-functional features, maybe VIC patch 1.04+ will do this:
Gas
Make "Gas Attack" a new battalion type to add to new inf divs and give them +5 Fire/+5 Shock no other bonus (Guards, arty, etc. would still have higher morale or org). Delete "Gas Defense" (Or, add a third invention that activates the gas battalion type while requiring all three 'gas' inventions to receive it.) Oh, and maintenance would be at least a 50% mod, maybe 100%+. The build time should be long and the resulting unit expensive in some way. It would also require Sulphur to build, since that resource is the closest thing to a chemical in the game. (New factory type, Chemicals?)
Tanks
Give a very late invention, 1910+, that increases their shock +5. Also, the first Tank battalions should have Morale -5/Org -5 since the early tanks were not that great nor did soldiers back then believe tanks were critically useful. The 1910+ tank invention would give back the morale/org (maybe). The entrenchment attack bonus feature need not be coded, just remove reference to it.
In my opinion, the other not-implemented features, like Diplomacy, are unneccessary.