I had a similar idea few days ago. It goes like this.

For a ceo to fill a large warehouse it will cost him 666k (37x18k).

If an mc fills his coke lab he stands to get 420k (not including bonuses).

So my idea is this. If you're playing as MC you get a choice. You can either sell your product in the same way you do now for 420k,or you can list it for sale and see if any ceo in the lobby is interested in making you offer. This would suit mc as he gets more money while ceo gets his product cheaper and thru less work. Instead of 37 missions to fill a warehouse,he now get it just by collecting it. Instead of paying 666k for it,he might have negotiated a 550k price.

Now here's where pvp comes in of course any big money deal between criminals is a tense affair. 8 mc members and 4 ceo. My idea is if the deal goes south and you get killed you are respawned a distance away. If ceo gets killed he drops briefcase. This is where the uneasy tactics come in. Does the ceo keep his buzzard nearby? Does the mc gang become nervous at the sight of buzzard? If all goes well,the ceo team roll out with product and mc go opposite way with cash. But now ceo location gets pinged to rest of map who stand to get 10k for stopping it. I think that's fair as the ceo should be taking extra risk as he is paying less than usual for product and saving a lot of time from doing missions.

This could lead to alliance being built. You know a certain ceo is trustworthy so you friend him and move product with him exclusively,until somebody maybe offers you more cash.

This way,the 2 factions can either come together to save and make more cash by relying on each other,or you could still sell the way we do now if you feel uneasy about trading with other players. I for 1 wud love to log in and receive messages from ceo in lobby asking if I have product to sell and negotiate a deal and a handover spot and rules. A President would also be able to see if a ceo had ever double crossed some1 b4 and stole product without payment. That way,the price would be higher,for example, if I had 420k of goods,normally I trade up with a ceo and get 575k for it but I see he has history of double crossing in his past,so now if he wants my goods I can ask for 650k or whatever. It will mean that ceo will really think twice about double crossing as it will affect future prices. Similarly a ceo can see if a president has double crossed in the past and again try negotiate lower terms. Imagine sitting in your clubhouse negotiating over text or chat with a ceo and haggling over price and meeting place. It would bring an exciting tense feeling to playing gta and rockstar still get their wish of loads of pvp.

I dunno what u guys might think of my idea but I think it would really enhance the game