[Imp]

It all depends on the player & has pros & cons

Cons
Yes having non combatant stuff in your core is not particulary sensible from improvement point of view.
You have to spend repair points to fix them.
Likes of trucks are a liability if defending as allows attacker a bigger force as you would not buy with support points as you are not going anywhere.
In fact as RERomine said most taxis can be a liability on defence even indeed armour, you could not buy scout vehicles as prone to dying if thats your thing.

Pros
Dont have to remember to buy them each time. I need x trucks x utility blah blah.
Means you have a genuine core unit capable of operating without support as I nearly always do in meeting engagments.
If plan on becoming mechanised sometime can now upgrade & already in a niceorder for deployment.
As a thought Division is probably getting a bit naffed off at you for keep on hogging all the transport.
Support is now just that divisional assets assigned to you so.

Every one has there own idea of what they want yours takes advantage of the game system but why not have a proper core & theme say

(Edit) sorry Gila forgot WW2 but you get the general idea just adapt from below to what you want so any extra armour would be TDs SPGs or such not tanks if look at big picture as the rest of your unit is already engaged.

If you want to take advantage of the game system I would say the things that benefit the most from experience are FOOs engineers (fast mine clearing) scouts & armour esp in WW2. Helos to in MBT if you can keep them alive as dodge SAMs better.

Russian 80s armour formation
Everybody has a ride inc HQ & is self contained formation with integral AAA arty ammo trucks.
Ammo dumps cannot be used in meetings as no time to prepare for onboard stuff & support arty air rare.

Support points are for divisional assets so AAA arty air engineers plus option of following.
Allocating extra ground forces
When available why not use troops local to area or in this case maybe have the Poles help out.
Can possibly recieve local scout or partisan milita support.
For urban get troops assigned as now you are really the support.
If need more armour no tanks available sorry in use elsewhere but can have ATGM vehicle hunter killer unit assigned.

Now you have a theme & a proper fighting force to take through the campaign.

If its a long campaign with upgrades no piecemeal upgrading you have to replace the entire company so save those repair points or your unit will not be among the first to recieve the new kit.