Hey,
I think that in your case, it would be best to start up the way Smokin Mils's dicing clan did back in '11.
When we first made the clan, we had a round of applications amongst the ranks of the merchanting clan. People could at that point in time still join in quite freely if they were ranks. They would pay a refundable deposit. Their set max would be a pot of half their deposit. This made it possible for us to start up, as people did not have to permanently invest a lot of money in a fc that might not become succesful, yet it safeguarded the clients from scams, as the ranks had a max that was lower than their deposit.
The ranks of the fc (recruit, ..., general) would show the maximum of ranks.
For example, a recruit could have a 50m eoc max, corporal 100m, seargent 200m, lieutenant 500m, captain 1b and general 2b/unlimited (best reserved for upper staff).
Of course you could have the deposit be more than twice the maximum to be safe, as otherwise it might still be quite easy for ranks to scam a total amount over their deposit. This was not much an issue within SM, as ranks themselves already held a degree of trust. I would suggest x5 would be sufficient.
It was required for all ranks to be able to provide proof of everything related to the trade for at least a week if asked, in case of a scam report (screenies/vid). In the end running a vid at 1fps or better of the entire process was required. At this rate, you still had a good proof of the trade yet it did not eat up one's hard drive even if you ran it for hours a day while hosting.
When a rank scammed, the amount up to one's max was refunded by admins. Not more, because if you would refund over one's max, a host could collude with someone to get vidded for "scamming" 10b, while it was actually their own gold. This would result in a succesful scam report in which case admins would've needed to pay out 10b.
All ranks also had to record their wagers (in this case swaps) on a google spreadsheet. 30% of their earning were paid to the admins as commission. If you were caught omissing wagers (swaps), one would receive a substantial fee, and if caught multiple times, a kick and loss of deposit. These commissions were first collected once a week. When we turned to buy-ins with a non-refundable deposit, this became once a month. All current deposit hosts would still remain deposit hosts and would not need to buy in, however they could no longer increase their rank by depositting a larger amount to admins. If they wanted that, they needed to buy in. When you will switch to buy ins, I'd recommend a 50% off for all current hosts.
Once you buy in for a certain rank, you could upgrade to a higher rank by paying the difference between said ranks in buyin cost.
As to someone saying that you'd need to spam the FC all the time with maxes: I'd recommend running an autotalking bot in the FC that spams the following every 30 seconds:
Welcome to R2Pleasent ~ Our current rates are [x:1] and [y:1]. Always make sure you're trading a rank!
Maximum rank limits: 50m Recruit,..., unlimited General.
~~~ I'll be grabbing something to eat now; Ill return to edit this further when I'm back