tank ridding

[AlienXXX]

Interesting !
But is it worth to put all the elements of the combined arms group in the same company ?
A leader is specialized in either arty, infantry or armor. So suppose the leader is paratrooper. He has to rally a tank, fails and can't rally anymore.
Am I missing something ?

If you are creating a "combined arms group" by deleting all elements of a company except the leader you end up with an in-game army made up of, say 50 "companies" of platoon size (i.e., the only the company leaders remain, all other units were deleted).
I have never played the game this way but understand these units have higher experience and moral so would usually be able to rally themselves.
If you do need the HQ to rally them, then yes, you could get into trouble. Not so much so because of the leaders speciality area (the HQ leader will always be stronger one one of the army branches) but because you have one leader controlling 50 companies...
The thing is, an army created this way, would have a great experience/morale advantage over a more realistic army (made up of standard companies) of the same unit composition and same purchase value.

If your question relates to the value of creating mixed arms units (e.g. infantry mixed with armour) in a classical command structure (say 4 platoons to one company) I guess it depends on the situation.
Say you have enough points to purchase 1 company armour + 1 company infantry, and want to attack throught 2 different routes with infantry supporting tanks.
You can do this by re-shuffling the 2 companies into mixed armour/infantry units. This gives you the command advantage that both attacking elements would be together and close to their leaders. I guess this outweights the inconvenient of having a armour leader trying to rally infantry and vice-versa.
Whether units of this composition are historically accurate or acceptable to other players is a totally different matter...