@Stormonu.
I think we agree on this then.
Bring back smoke ,(and Bind), shells, grenades and mortars.(In a carefully applied way.)
As this adds the tactical option to units that can not possibley take out a heavy tank for example.
They now can drop smoke on the tank, to make it difficult for the tank to target friendly units.Or directly in front of the smoke firing unit to improve their own chances of survival .
Cover, smoke, smaller size, (and may be range?)Making units harder to hit at range is sensible.
A simply applied suppression mechanic allows infantry to be important, and have tactically different uses to vehicles (and
MCs).(Like all good war games seem to do.

)
@Charistoph.
I would like to try to get the flexibility and thematic feel, found in the good formation/detachment set up as you pointed out.
But arrive at it with a simple core F,O,C mechanic that can be easily be used with multiple themed lists.
You posted..
''Where I think
GW went bad with Formations is that the Special Rules that come with them make them a no brainer, and then compound the error by adding on the Command Benefits provided by the Choice Detachments. Seriously, why should we have to have Special Rules for these Formations, and if we should why should they have the level of power that most of them do.''
I completely and totally agree with you on this.