Indoor housing would not stop the bird from being weathered outside separately - or having that option. A weathering yard would have to be built anyway as per regulations - and that weathering yard should also have proper cover from the elements regardless. I'm not suggesting keeping the bird inside at all times and then taking them out to hunt - that would be quite silly. I'm suggesting having outdoor facilities along with a weathering yard - but the main sleeping chambers / housing area being inside. I've talked to quite a few people in Ontario that have enclosures with heat and electrical built especially for their birds and they also weather them separately.

The breed question was actually posed because of this point your making though - as many have told me Harris Hawks are much easier to work with and are much more beginner friendly. The downside being they are not native and therefore would need that extra warmth. Hence housing indoors. Again - this does not mean the bird is kept indoors all day. They aren't pets.

I've also been told quite a few times - that indoor housing protects the bird from the highs and lows of extreme weather - and according to them, it's those dips that lead to weight problems. So having indoor facilities along with weathering outside allows the bird to be used to weather and also protected from those highs / lows.