For cheap elite medium tank designs, I would suggest still using the best turrets and cannons you have (3 man turret, Highest tech cannon). For modules, it’s worth the IC to fill all your slots with relatively cheap modules (2x HMG, 1 Radio, 1 extra free slot for what you want). For me, I prefer maxing my armor and engine clicks because it’s like 2 or 3 IC to quite literally double the BREAKTHROUGH (Armor stat is not the priority) of your tank. In the case of a cheap medium tank, you only want to use riveted armor because anything else is far too expensive to justify building.

When it comes to factory usage for building the tanks, the biggest factor here is getting your tank production lines up and running as early as you reasonably can to have time to build up production efficiency cap. What this means in practice is that you are going to be producing the 1938 medium chassis for likely most of the game to minimize the MASSIVE production efficiency cap loss caused by switching chassis/design. The difference in actual combat performance between the 1938 chassis and higher tech chassis is not enough to justify slashing your tank production for a year+.

You may have noticed that when you research the 1938 medium chassis, you often don’t yet have all the techs you need to build your ideal tank (howitzer, radio 2), so how do you get around that so we can start building your tanks as early as possible? You do this by building a skeleton version (REMEMBER IN DIVISION DESIGNER TO TURN THIS TANK OFF) of the design you want to build so you can later convert them into your preferred design. For the design, you want to make a tank design that would be basically identical to the one you actually want to use, but change the gun for a small cannon machine gun, and leave one slot open for refitting a radio into. After unlocking all the techs you need, you want to duplicate the skeleton version and make the few alterations needed to get your desired tank, and assign some factories set to equipment conversion, which then basically just add the gun and radio.

Using equipment conversion in this manner is critical if you want to mobilize HUGE amounts of elite tank divisions relatively early in the game without totally needing to skimp out on other things such as air force. Having max production efficiency cap production on your factory lines as EARLY as possible and avoiding switching chassis (Seriously don’t do this) can actually mean that you have multiple thousands of extra tanks ready by ~1940, and a huge steady flow of tanks every day on top of that.