Yeah the amount of investment one has in a system may explain the rather ‘angry’ sounding comments one encounters when daring to suggest that system X is flawed and/or not suited for a given scenario … (which is why I love the OTT community as we can discuss things without flamewars and cursing 😀 )

As for the ‘armour’ classicifaction … I’d say anything that requires specialist weapons/skills that are not used by the standard troops.
A half-track could qualify if the enemy had improvised weapons bows and arrows …

There’s always a chance to game the system if you can throw enough dice at a problem, but I’d argue that you wouldn’t be playing by the intent/spirit of the system.

40k is kind of a special case, because they are dealing with a gigantic legacy and a fan base that is resistant to change. I’d also argue that GW isn’t interested in designing a clean system either as their motivation is more like “new shiny sells”. We got lucky with 8th edition, but within months after launch it became clear that there was no plan to keep it balanced in any shape or form. With 9th we were back to the need to keep the game ‘visible’ as opposed to actually fixing stuff ( … ).

Companies like Warlord, Battlefront and Corvus Belli tend to have better motivation as to why changes in their respective rules happen (streamlining, fixing flaws, making stuff easier to use, etc). Maybe they are better at communicating these changes, because they need to be ?

Anyways …

It’s always important for players/buyers to be aware of the intent / design principles of the system they pick.
It makes it easier to deal with flaws if you know that you’re effectively doing stuff that the designers didn’t consider … (like fielding a couple of Jagdtigers by min/maxing your armylist).

Then again … emergent gameplay can create interesting results too.