Like a few others I don't see any realistic reason why you should make income from the people working in factories making weapons and facilities for the government, that stuff costs money, and should be a drain on your economy.
I think whats needed is a more robust civilian sector that builds upon what already exists without a complete game changing overhaul as proposed.
Actual numbers would need to be tweaked and tested, but my proposal is that you should basically be balancing 2 types of economy, First is your wartime physical economy, building factories, ships, training people, moving stuff around etc.
This stuff is expensive and is the primary thing most people spend their time on none of this stuff should make you any money, but rather you trade money for its productive output.
The other half is the monetary economy, producing a robust civilian economy that can provide the liquidity for employing the vast amounts of people and resources needed to run production. This is commercial enterprises, right now only CMCs, fuel harvesters, civilian trade, and taxation. As of now CMCs and harvesters build up slowly, trade can take a long time to get flowing smoothly, but population can easily reach the point where hoarded wealth becomes irrelevant.
A wealth cap was suggested, I don't remember the specifics suggested, but it seems to me that people should be encouraged to balance the economy, right now theres a major crippling disincentive for reaching a deficit (which I believe should be heavily reduced) but theres no system encouraging not reaching a surplus. A wealth cap would do this since having extra wealth is just wasted, perhaps there could be a tax rate which could be set exchanging higher population growth or something for less or more wealth generation.
All population shouldn't produce tax income, the service industry should have the highest wealth output but it shouldn't automatically produce income. Rather than having a flat percentage of population is "service industry" anyone not employed by the factories etc should be considered unemployed and generate no wealth, your service industry which does pay taxes should slowly grow based on things like trade, morale (not having ground battles taking place on the planet etc) and so on, in any rate the service industries should never grow to a higher percentage than the number of people employed directly by the player, consider this the trickle down effect of the wealth from government jobs being spread around.
Then finally financial centers should help to raise the wealth cap, help increase the percentage of the service economy, increase trade, etc.