There have been comments, on various threads, about how most tournament armies are 'core plus cavalry support', as that gives a better chance of winning than a wholly infantry army. Here is a suggestion for encouraging (or perhaps I should say forcing) players to have an infantry support, at least where only one support option is to be used.
At the start of the game, before attacker and defender are determined, each player throws a die, and unless both are greater than or equal to eg 4, neither player may choose a support brigade in which the majority of non-artillery units are cavalry units. Note that the somewhat convoluted wording is needed to allow eg the Brunswick Brigade or a Russian Reserve Artillery Brigade in an 'infantry' army but exclude the French Cuirassier Brigade (1813) which has equal cavalry and artillery units.
If adopted, this would mean that many games would have infantry support brigades, which doesn't happen very often in tournaments, I believe. Of course, it means players have to bring both a cavalry support and an infantry support, but at least there would still be a chance for a player to use the pretty cavalry sometimes, rather than just banning cavalry supports entirely. Note that if the dice are both 4 or more, neither player is required to have a cavalry support, but they can choose to have one (as I guess most will).
This idea can be developed further by having modifiers to the die roll. Those armies which historically did not have much cavalry (British?) could increase by 1 the die roll needed to allow a cavalry support, so cavalry supports could not be chosen unless the British player rolled 5 or more, and armies which had more than average cavalry (Poles?) could decrease the roll by 1. If the requirement that the die rolls are 4 or more gives too few cavalry armies, it could be 3 or more.
I also think that the definitions of decisive/marginal victory would need to be changed to prevent those armies with cavalry in the core force (Austrian Avant Garde, French Peninsula) having an advantage. I have never understood that rule for a competition; why does choosing an army with lots of pursuit cavalry make me a better general? A simple varient could be to say that a victory is a major one if the victorious army has not lost 20% or more of its morale point value, otherwise it is a marginal victory. That works whether the army has cavalry or not.
Of course, some people will not like having their support choice restricted, and no doubt there is a flaw in this suggestion which I haven't appreciated. And it isn't needed for 'scenario' games. However, I can say in favour of the suggestion that it doesn't actually change any of the rules in the rule book (apart from the victory definition change, which I think is wrong for tournaments anyway) so has fewer knock-on effects than other ideas for increasing the types of armies which players use.