What is the difference between your project with the P&L service that those exchanges have?
I'm curious about the "more accurate" part and what it could offer me if I were to avail your service.
The problem with PNL tracking on most platforms is that they fail to separate funding payments from realized/unrealized PNL. This means you will not know what portion of your PNL is attributable to funding and which is simply from gain/loss. By separating these metrics, you can focus on optimizing your funding rate earnings. For some delta neutral strategies, the PNL from gain/loss is mostly irrelevant.