Some things "off the top of my head"....
1) Basic unit should be the battalion and perhaps cavalry squadron.
2) Greater use of battalion guns which suit more methodical, linear style of warfare
3) "Corps" is not relevant. It could be the entire army but if we go to a "battalion" as the basic unit that armies might be too big, so perhaps "wing". Although these were not designed to be balanced, all arms forces. So it should be a player's "C-in-C" commanding with the FoG(N) division commanders replaced by brigade commanders.
4) I have no problem with a double rank of figures but the options should be between "line" (i.e., four bases wide and one base deep) and "march column" (one base wide and four deep). The former for combat and the latter for moving to the combat zone.
5) Infantry should be relatively impervious to cavalry from the front - same as the square for FoG(N). The bayonet replaced the pike without the need for "squares".
6) Light troops mostly restricted to "irregular".
7) Common use of field defences by some armies.
8 ) Infantry that was disciplined and held its fire until the enemy infantry was close seemed have the upper hand.
9) Less maneuvrable 'battery" artillery.
10) We may need to think about the tactics used by cavalry of the different nations.
This is from Don McHugh's WRG lists for the 7YW (Europe), from 1992 in the section where he explains the rules adaptations for the WRG 1685-1845 rules. (By the way, Don, complains that as of that year, that there was no easy to play set of rules which reflected the linear tactics of the period.) From the Rule Adaptations section:
"The main alteration to the rules are centred around the linear tactics used by the infantry of the period and their extensive use of battalion guns, which when combined gave them the ability to repulse cavalry by fire, without the need for forming squares. This, however, required a prolonged and very high standard of training which was not possible with the hurriedly conscripted massed armies of the Napoleonic period.
"It is true that towards the end of our period the increases in artillery pieces had led to the use of grand batteries, but the use of columns, although experimented with by Frederick were far from common. Artillery had greatly increased in an attempt to compensate for the falling quality of replacement troops, but these larger numbers made armies less manoeuvrable and so created other problems. The Prussians tried to overcome this with the first attempts at horse artillery, however, this was unsuccessful as it could not move fast enough to keep up with the cavalry, but was faster than the infantry and so ended up between both, unsupported by either, and easily destroyed. The numbers of light troops increased also, but they were still employed mainly on the flanks in a scouting and harassing role or to occupy difficult terrain, such as marshes and woods. The Austrian grenze were masters of this art and caused Frederick great problems, so much so that he tried to raise his own light troops but with little success. He was, however, successful in combating their hussars, and achieved this by training his hussars to fight like dragoons and not rely on skirmishing tactics."
That may not be the final word but I thought it useful to quote the thinking of someone else who attempted to adapt a primarily Napoleonic set of rules (even if it claimed 1685-1845).[/quote]
Thanks very much.
This is a really useful and helpful summary of the issues to be addressed and modelled- and expresses more clearly than I had many of the things that need to be catered for . Not for the fist time in wargaming someone ( Don McHugh) has been there before!
Taking it forward I guess what is needed is a short paper on " What warfare at the front edge of the battlefield was like", key and common characteristics of encounters between the component arms of infantry of the line , cavalry of various types and artillery ,their roles an functions and where it was different in different theatres. There is stuff like that in the FoG(N) rulebook which I originally wrote just for us to use as a summary when we kicked off the work in 2008. (We put it in for any readers who might be new to either the period or wargaming as a whole). I see a big bill to increase my library coming on
Which is another point - who do we want to use these rules - existing afficionados ( who will be relatively fewer in number than Napoleonic I would guess) or people wanting to try it out who have not done so before and so to spread interest? The former will be harder to please totally - as I was even with my own rules in FoG(N) being a dedicated Nappy Nerd

The latter will want something easy to use - er - and fun rather important

.