Thanks for the clarification Marshal.
By the time you are getting to level 13 or so, you can't afford to have any unprofitable or low-profit corps in your country(ies), which includes corps that employ a lot of LLWs. But by that time, your education index is such that you don't produce a whole lot of LLWs, so worker balance is not a problem - you don't need to worry about finding employment for the LLWs either in the army or in corps, because you don't have that many unemployed.
You need a DI of 200 to reach level 15 and FI of 140, so you have a choice. You can put high-points-scoring (but pretty useless on their own) weapons in each country (MIBs or defensive radar planes), using the fewest workers, and gear the rest of the economy to making as much as possible to get your FI up. Or you can put all the same weapons in just one or two countries, which will have lower FIs, and leave the rest making as much money as possible to average it out. Either way, the result is pretty much the same.
If you want a war slave, however, with weapons that are actually some use (fully garrisoned and with an adequate offensive), you can only sustain that in around 10% of your empire. The other 90% of countries have to be purely econ in order to bring the average FI up to what you need for level 15. An effective war slave will be lucky to get its FI over 70, even with all its corps maximised, so the other countries have a lot of extra FI points to make up.
Xlong - the skill in this game is to build an understanding of which variables affect which other variables, just as it is in chess. With chess, the variables are the relative positions of the pieces and how they do or don't protect each other and form a good offensive position. With Simcountry, you aren't necessarily facing an opponent, so the variables are more internal. But the principle is the same. The fact that it is so complicated is what keeps most of us playing more than a few months
Hugs and respect
Jo