I think generally the rules are sound, I'd like to see them tightened up a bit and have some plainer english to clarify some rules (War engine splitting CC/FF attacks for example, the ever present scout screen vs air assault circular debate, within vs entirely within on dismounts etc)
I could not disagree more on the countercharge rules, right now it adds nuance to the game about where you position units, and also how you set up engagements, with the dismount distance, if you could always countercharge towards the engaging enemy it would make it much harder to set up effective support fire and clipping engagements. It's perfectly well rationalised from a real-world perspective too as the ground scale is not linear, 15cm represents ~250m, 30cm is 1kM, when a company/formation is spread over that kind of distance, it would be perfectly understandable for the squads closest to the enemy would refuse to turn their backs on the enemy and run away....
I like the simplistic way war engines are handled personally, with suppression not affecting them until they break
In terms of rule changes I'd be interested to see a splitting of the reinforced armour rolls, so you could have it be
Reinforced Amour(X) where X is the re-roll value
for example a warlord titan would have a 4+ armour save (or maybe even 3+) and reinforced armour (4) so it would behave as it is now, but a leman russ might have a 4+ armour save and reinforced armour (5+) it enables list writers to tweak the units a little more.... it's far from essential of course
TL;DR I'd want to clarify most of the 5-min warmup questions into concrete rules interpretations and fiddle about with armour saves