Another piece of feedback is that the order listing REST API is not so good. We can list every order via /api/v3/brokerage/orders/historical/batch, but we cannot filter by only the open orders (which has got to be the most common case). Instead, we can only filter the order_status by closed statuses.
A better way IMO would be to have an endpoint at /api/v3/brokerage/orders which does a similar thing to the above. Instead though, it could have a main order status field of order_status with values [OPEN, CLOSED, PENDING, UNKNOWN], where there could also then be a order_sub_status field that have values {OPEN => [UNFILLED, PARTIALLY_FILLED], CLOSED => [FILLED, CANCELLED]}
This would allow us to easily see every open order (or a subset on those partially filled, unfilled), along with every closed order (likely filtering by the ones that have been filled).
Of course, we could avoid two levels of statuses as well, though it would just mean having to add the appropriate filters (similar to what there is on the orders/historical/batch endpoint, but actually allowing filtering by currently open orders).