I’ll tell you one way to have it.
Usually a “paymaster contract” refers to gas being paid for by a smart contract - in exchange for an amount of ERC20 token (e.g. ANT) valued at least as much as the gas costs. This is a good step forward but not “gasless”. It can, for example, help someone who’s ran nodes & earned ANT - they can be empowered to transact without having to figure out how to buy & move ETH to their rewards address.
To achieve nearly-gas-free, consider Payment Channels. Bitcoin’s Lightning Network is a good example of this.You can look up “lightning network micropayments” to get an idea.
Basically, through smart contracts and off-chain transactions, payments from clients to nodes can happen. Payments would typically be routed over a few hops - each “payment transmitter” (or “bank” - whatever you want to call it) would charge a percentage. If this is architected well by the team that implements it, there could be a smart contract that serves as a registry for listing banks, their routes and fees (for routing payments to connected banks). It would cost some collateral to be listed on the registry, which would serve to ensure compliance.
So, instead of Autonomi nodes receiving an on-chain transaction (to their rewards address) for every data payment, they’d have one or more payment transmitter channels (“bank accounts”).
Gas would only need to be paid when moving ANT in or out of a “bank account”. Also, a small amount of gas would be paid by banks when they settle their inter-bank payment channels. e.g. a bank called “Barclays” originally set up a payment channel with a bank called “HSBC” with 100 ANT collateral and has routed a few million small off-chain debits totaling 100 ANT - the channel is settled on-chain with one transaction for 100 ANT.
Depositors / payees could always withdraw their funds at any time. It would cost a little bit of gas however (and perhaps the gas is payable by ANT).
Basically, as data payments come in, node operators would receive “receipts” from their bank account(s). Each receipt would be for a greater amount than the prior receipt, and a receipt could be used to make a withdrawal from the bank (via a smart contract that doesn’t need further permission from the bank). The receipts issued to a payee (Autonomi node operator) would all have the same nonce, so that the payee would only be able to redeem one receipt that has that nonce - preventing double-dipping.
It’s worth noting that these “banks” would need to use p2p communications with each other that are feeless. I don’t think ScratchPads are appropriate (fast enough). The banks don’t have to use Autonomi itself for their off-chain ledgers - that can be a separate layer (but I don’t know, maybe Autonomi’s current client networking libraries could support this use case as-is). Either way, I believe nearly-gasless is totally doable.