Your case is more complicated than just wanting the remote Thermostat sensors.
The remote Thermostat sensors you speak of are currently shown in the store with a projected availability of ‘2021’, changed from ‘early 2021’. So don’t expect first shipments until very late in the year.
Manufacturing is the one mostly affected by the chip & labor shortage, which delays the first shipments. Just ask anyone with a current pre-order.
There are some Wyze ‘climate sensors’ that are available for pre-order now. Unfortunately, they require the Home Monitoring Hub, which is currently only available for WHM subscribers.
Also, whether either one of these sensors ever get rules is TBD. I think the climate sensors currently only have alerts.
In any case, the climate sensors are only recommended for indoor use, and I wouldn’t expect any different from the announced thermostat sensors. So that could be a complication for your outdoor air measurement.
OTOH, since the use case you outline is mostly a seasonal thing, maybe a simple high wall fan to the attic might suffice for the summer, and a damper to a vent next to that could control whether the low vents or that high vent feeds the furnace in the winter? I don’t know whether you can get modern Bluetooth versions of those, but even if they were controlled by a drawstring or wall switch, if might be enough?
I have a very similar situation myself. For me, I helped the summer situation by installing 4 motorized clerestory windows that at least allow me to vent some of the hot air to the outdoors. However, because there is no fan, that really only works for me in the spring & fall. And there is no solution for winter like your idea.
Your idea sounds more comprehensive, so I would love to see what you come up with, regardless of the vendor(s) you use!