So basically the command /sw nation paysoldiers exists, but problem with it is, being a "soldier" in a nation is not very specific.
This is also completely limited to the military.

I do not know how the plugin works therefore i do not know what is the easiest or even the (most possible?) way to make this work, but the whole idea is to be able to distribute salaries to specific group of players.

Example of this could be, organising town members to help build walls and then doing something along the lines of /sw town paybuilders 5000

This could also be divided for titles too, for example, if your nation uses titles that represent ranks, you could have a different pay for different titles and therefore a good reason for players to keep titles functional and reserved.

example of this would be, after a siege deciding to divide 10k among 10 "Privates" and 6k among 3 "Sergeants", this feature is kind of already covered with generals getting different pay than soldiers, but what if you have "Militiamen" "Footmen" "Warriors" and "Knights", its simply convenient to be able to at the same time manage town financials more efficiently while being able to give meaning to tiltes

And yeah, if titles thing is just too complicated or simply out of question, then simple town version of same command should be enough, so its not always entire nation.