Scale and rules are not an issue and quiet likely most rules have a Waterloo based scenario.
Waterloo is possibly the most written about battle of the Napoleonic period and features in film and TV and even song. It is well represented by games. More than most battles, this is one significantly affected by hindsight and also perhaps minutiae of reported (real or otherwise) factors affecting or occurring in the battle.
The Order of Battle is well known (with a bit of latitude for losses to units that fought at Ligny and Quatre Bras and potential for stragglers).
The initial deployment is also well known and most games I have seen start with the 11:00 deployment which was around when the ground was drying out and the assault started on Huoguomont. What I have seen is that the initial deployment is very congested perhaps suggesting some divergence between ground scale and the footprint of various combat arms and formations.
The terrain you would think is also well known, but there are many maps/drawings and they seem to vary a good bit as I found out when I was doing my research:
The terrain has three factors (ignoring mud which is probably assumed to affect both sides and result in the delayed start of the battle);
- Fortified farms and chateaus
- Reverse Slope vs hills
- Hedges and sunken roads
Getting the size and strength of the farms and chateaus right is tricky. Too big and they will dominate the table, too small and they become non-viable for holding the required number of troops. Too strong and the French player will do their best to avoid them, too weak and it won't be Waterloo. I'm still tweaking the size and defensive factors for these positions.
The term "gentle slopes" is probably best to describe the land. It provides cover from artillery bombardment rather than a defensive position per se. Because they are not discrete hills, but slopes, they can be a challenge to represent. I used a contour map, but I'm currently attempting to review the contours in use.
Hedges and sunken roads vary in importance depending on the tactical level of the rules in use. I left them out of my game on the basis of including their effect as part of bolstering the size of the built up areas, that they would affect both sides and ultimately be represented in the variations in die rolls during combats.
Prussian arrival timing and order of march is another challenge. This is highly dependent on table size and movement mechanics. There is also the question of the French, with the benefit of hindsight, being able to interdict or at least establish strong defensive positions.
Commitment of the Guard is possibly the most telling factor to be affected by hindsight. With the knowledge that the Prussians are coming and assuming battle is still to be given, should the French player commit the Guard as soon as possible? In the two games I have participated in the Guard was held back by the French players, without the need for special rules.
My final observation regards the cavalry available. The French have have 15,600 with two corps and ten divisional cavalry commanders while the Anglo-Allies have 13,350 with only one corps and one divisional cavalry commanders. Representing that is tricky.