[Imp]

I am just going to make a couple of points.
Firstly list 2 battles where 120 Tigers took part.
The battle frontage for a 200 deep map is 10Km & while the Germans would have loved that a realistic proposition would be 25-30 MkIII or MkIV against an entire Russian brigade of T/34s.
That would be an everyday Eastern Front battle the Germans never getting up to full strength as tanks constantly in R&R.
The Russians would generally get decimated disband & throw a whole new unit at.

If you really need an Ubber force of 120 Tigers you are not playing very well.
In real life a lone Tiger has held off 40 T34s more than once. Admitedly they chose good high ground to do it from but there biggest problem was running out of ammo. There is even an unconfirmed case of the tank commander standing on top directing while being passed rounds from an ammo truck behind the ridge line.

I would say the reason for the large varience in AI purchasing is its trying to add variety & does seem to buy according to terrain. If you ignore the wide range of vehicles rather than just a few types its buying is probably a lot more historically correct than yours.

Try letting the AI buy for you.
It does tend to buy in a messy order but everything tends to be there & have won PBEM games with what it gave me.
More obvious in MBT but tailors to map type so
City map I got virtually no MBT but lots of troops AT weapons & light tanks who could quickly move to ambush positions.
River Crossing 3 companies of paras in helos more in air transport cant remember rest but think had only 1 company soldiers on the ground & a platoon or 2 of tanks.
I would never have risked so many units in the air. Result by about turn 5 my tanks were crossing & mopping up.

Dont play AI much anymore but if do always let it have the best gear or give it double your points. It is not capable of moving for flank shots organising combined assualts etc. but buying is generally OK. If used all the time I would like it to buy a slightly higher ratio of top tank but hey variety makes for a challenge.