the ability to remote the anemometer from the sensor body.
That is a good point. My previous setup had the anemometer up a 12-foot pole, and the other instruments at a more convenient level. Even on a pole, my wind speed readings are about 50% of actual, due to surrounding trees, so I was thinking I would have to mount the Vantage Vue up on the pole to get reasonable wind speeds. That of course means that the rain gauge is impossible to clean of leaves, spiders and snow. So a detached anemometer is a big plus.
generally separate sensors are a good idea as you can optimise their location, remember maintenance access and allowance for your weather!
But you also have to remember the transmission distance.
My fineoffset system manages 200ft in one direction but only 60ft in another due to walls in the way!
You can vary the location of the gateway unit (if you go that route) or console so you can play with router to gateway to sensor variations
I recommend a dry run in rough intended locations before going firm and leave them for a day in case there are day/night variations
If you go the fineoffset fgateway unit route it's very small (matchbox size) so there are loads of options for putting it outside under cover (it's not waterproof and does need a usb supply) which might make sensor to gateway placement easier, as long as the gateway can find the router. I put ours in the conservatory next to a window which worked really well with the sensors (direct line of sight and only a window in the way)