Yes Dorowar my token system works really well. It adds a mission based element to the game that probably can’t be duplicated with any other type of house rule. It is such a game changer that you don’t need to put in a bunch of other house rules. Rolling the D6 first and then choosing the chart takes more chance out of WD than you might think and everyone should give that a try no matter how they play R&D. My guess is your play group will want to adopt that for sure.
I don’t know if you’ve ever played the 1914 Tournament Rules, but they have something there that is a specified threshold for each nation that puts them in economic collapse. Perhaps an idea for you might be to determine an IPC level for each nation that must be met in order to develop weapons in lieu of NO’s. That is kind of the same thing as what I do - force a nation to be worthy of developing a weapon. That combined with your research token and some cash and you start rolling for a weapon.
Whatever you decide to do let us know how it works. Some of the best ideas are the ones we get from others here.