The problem with lance armed Imperial Cavalry as a concept is, that it is to much reminiscent to the knights of KoE and that the difference to EoS might start to blur if Imperial Cavalry is too strong. My personal wish would be to turn the Reiters into proper core front line cavalry by taking away Vanguard and giving them access to plate armour or fancy guns. This way you would have unit reminiscent of historical 17th century cuirassiers, a unit which is distinct enough from KoE. Vanguard might be provided by new Dragoons and Lancers might become an elite bodyguard or something. In this way everybody can use his models without stepping on each others toes fluff wise. Knights stay knights and EoS has interesting core cavalry. But this is just a suggestion.2. Imperial Cavalry. Checking our ASAW we have an "all cavalry" as a playstyle and First Turn Damage output as major weakness, and it's quite schizofrenik. If we want to field upgraded cavalry with lances, they cost us 50 ppm, that's the cost of WoTG knights of Ryma ones. Yes, our ones are from Core, but we don't have any alternative! KoSG are good, but they have no sence of fielding them with more than 3! Either we need to go from army with Cavalry playstyle (and it will be VERY sad), or we need to reduce the cost of additional knight a lot. MAybe, the good solution will be, that with Knight Commander they become 10+ unit and cost 20 ppm less? SO, the unit of 15 cost like 500, not 750. They are still way worse in attacking than many of the analogues.
3. Reitars. They are used so much not because they are SO effective, but because it's the only Unit with Vanguard we have. Rangers fit the same role, but from another angle, being slower, but having Skirmishers. It's OK to have such a low numbers, because we have Special Deployment as Weakness too. But impossible to play without chaff at all, and we don;t have any flying MC or light troops heroes for cheap. Cut their effectiveness ,and we are in serious trouble.
And both kinds of units existed at the same time, though I think that cuirasiers/reiters were a bit more numerous in the late renaisance period.
Reiters are good as they are and would probably become too good if they had fullplate.