Some brainstorming, also typing out the potential stupid stuff.
Premium maps
Maps which are out of beta phase, ready to be deployed. For some time only premium players can play them - a month or so.I thought about premium servers, but that would probably split the players up.
Eco system
The hole game has a money system. You can apply for a contract, and thus earn money by playing a map. You do get better, and as such you can get more money.
This would only work, with a accurate matchmaking. Even if the accuracy is - to know that we do not know yet a players skill.
As an example, my skill is 20/100 - I start the game, get the serverlist, and it shows me all servers with a higher skill in red - if I play there I get extra bonus for each thing done. Those with a lower skill are marked white, and I will get no Bonus.
The contract I talked about is done automatically. Its not like I have to sign up a contract, and wait for the game to start.
The prob I see here is the competition - but more on that later.
Skins
Are kinda obvious a selling point. But it has the potential to make the game unbalanced. Since we need to be able to recognize a merc.

Weapons
Uhrm no idea… the more that is being tried to monetize the more I guess its unbalanced. Proof me wrong please 
Competition
For competition you get a “virtual” sponsor from that Eco system mentioned above. Thanks to that sponsor you can get any merc type or weapon upgrade. At best some real companies would play the sponsor role - at least skin wise (advertisements=).
Second sponsor type is a clan, which can act also as that. And they can on plus have multiple sponsors, else they have to “pay” themself - either real or ingame money.
Bets
With the ingame money bets can be placed on competition matches.
(I guess as long as the ingame money cannot be transfered back to real money - it should be legal everywhere?)
Statistics
Premium members can keep them forever. Going from that, one which does not pay anything gets also stats but not as detailed after 7days or something like that.
So whats the deal with premium, lets say you pay every month 10$ for premium account. That would give SD a stable income, which they can more or less guess where its going too. Basically I saw that “premium” on battlefield I guess, and I think its a title wished by many.
Now everything should be payable with ingame money. So that if somebody is unemployed he can pay with ingame money that premium account and so on. But then he really has to play a lot.
)