One thing I liked about World At War was that you couldn’t all of a sudden get Rockets in one turn. In WAW you have a progression. Everyone starts at 0 for every technology. To advance you pay $2 and roll a die. If you roll a 1 then you move your counter to 1 on the technology sheet. The next time you pay $2 and you need to get a 2 or less. It progresses until you reach 5. You can get technology immediately but its not nearly as easy and on average would cost a whole lot more.
What I would like to change however is a blended national advantage and tech chart. So you would have heavy tanks available for everbody but instead of starting at 0 for germany, she starts at a 3. This way the german play can choose to progress that advantage or not. I haven’t tried it but you could also make this vulnerable to SBR too. Careful not to make it too easy to knock out tho.
So you end up with a technology/nat advantage of lets say Long Range Bombers
Long Range Bombers allows Bombers to move 8 spaces
USSR starts at level 2
Germany starts at level 3
UK, Jap, and US start at 4