As another answer says, since you have any level of deliberate visibility into PANs, you need to meet PCI requirements.
There are structural carve outs, like ISPs do not have to submit reports on compliance for PANs transiting in the clear over their wires, because those PANs are the responsibility of customers of the ISP. But the question describes a clear scenario of minting and exchanging PANs, so you can be shown to bear responsibility and should maintain a compliance practice.
The level of compliance is dependent on the number of transactions you participate in, which in your case since you seem to see the PAN on every cardholder transaction, could be substantial. There is also a material difference in compliance requirements that depends on whether you are "storing" the PANs "at rest" or just working with them "in transit", with the latter involving fewer requirements.
It sounds like you should be able to keep your compliance to the in-transit conditions, however you can easily find yourself with an at rest architecture if you do simple things like "temporarily" cache PANs in a redis.
That all said, I am curious about one thing- with whom do you need to have this compliance relationship. It should be through the acquiring bank backing your card issuer- if they are not themselves a bank- and your contract with the issuer should contain language to this effect. If it does not- if you are already in this business and you do not currently know to whom or with whom you need to submit a RoC or similar, you may have created a lot of liability for yourself.
PCI is fundamentally just a bunch of commercial contracts, not a governmental regulation like HIPAA. If you are participating in the minting and exchanging of PANs and something goes wrong and you have no contractual provisions and protections around this, or insurance that covers you for this, a lawsuit will appear that will put you out of business.
I would advise going through the language of your agreement with your issuer first, there has to be something there.
