Well, you can turn 4E into a business. As the head of 4E, you're in charge of buying "inventory" to improve the efficient of the company. Use the money to buy new weapons, buy new recruits (payroll btw), buy new vehicles, etc. Though, doesn't the purchasing manager do these?
It may be more efficient to just have money at the end of a mission to satisfy all players. However, if it is going to be challenge based, I guess it has to evenly spread out to accommodate all players. I guess you can look at GRFS challenges. It seems to be balanced out for stealth and action players though GR has never really been about stealth plays.
I guess getting money has to be about stealth plays, I mean it is Splinter Cell. BTW, it seemed that Conviction was pretty balanced in the challenges or PEC so Blacklist may have something similar.
Besides, I guess the devs can figure out how to balance out the money system for all players.
I don't particularly like money system, look at Black Ops........lol......I just don't like spending money and having to pay for my unlocks. I want to earn them or just be given them.