First of all to the AGEOD team: I'm really enjoying your games. Your games deserve to be called STRATEGY games.
Playing AACW at the moment, I wonder if there will be a Grand Campaign stretching from 1850 to 1920 in VGN. I'd really appreciate that.
I consider myself an "empire-builder" and for this reason I love to be in control of every aspect of the game. The grand campaign in AACW comes very close to what I call perfect gameplaywise.
As the game is still in development I'd like to share some thoughts with you:
As research was conducted mostly by private enterprises during this age, who offered their inventions to the government and the army/navy for approvement, I'd like to see a rather abstract research system. There could be an event saying an inventor states he developed a new artillery piece and offers it to your army. Then you can decide whether you want it or not. If you choose yes, there's a cost for setting up the production (in money/WS). If you choose no, the piece will be available sooner or later, but pieces may be more expensive.
If you aren't satisfied with your artillery's performance on the battlefield, there could be political, military or civilian option saying "encourage gun development". This could lead either to availability of a new type of gun a bit sooner than historical (but no railwayguns in 1851) or better training (more xp for units or a random statistic increase +1).
Of course there should be more options, but only one could be enacted per year and field. So one for the army, one for the navy and one for the economy, for example.
In a similar way options could be a way to build up the economy. For example there could be an option "government supports armaments industry". Then there's a chance a factory, foundry or whatever appears. I liked this indirect way of industrialization in AACW, because there was no pure state economy in the peroid. However I missed a tooltip saying how many chances a city has to get an improvement and whether the chance is 5% or 10%... In VGN I'd like to see that you can enable this kind of options in certain regions if not provinces (I'm not quite sure how many provinces/regions will be there). Then the option could be "the government invests in military infrastructure in northern France or even in Lille, for example.
As there was quite a lot of advance in many fields of research during the timeframe, I wonder how upgrades are made. I vote for two options: first you should be able to upgrade all you units at once (of course limited by your treasury) or each unit individually. I could also imagine that upgrades are paid for in replacements which you have to buy first. This would add to my control obsession

If the GP makes it into the game, consider it bought!