how about if we bring a BMD Smart Videohub into the picture?
Routing all of our feeds and converting them as necessary for our stream? Will the same case apply in the event that we want to stream on 1080p a feed from the cameras that push 1080i at max?
Are you expecting the VideoHub to do the conversion? Because that will not be able to do any conversions. It can only take the signal it's given and route it to the outputs. You will have to use external cross converters for every signal you want to change from one format to another.
Also, at that point it would possibly make more sense to just replace the ATEM with a newer model that can do 1080p.
In summary, since there is not a possible way to stream native 1080i 59.94 resolution from Livestream Studio (is there?) it will always be better to input 720p instead of keeping the 1080i input (which will make the encoder software downscale) or upscaling to 1080p through a converter. Right?
Livestream Studio can actually handle 1080i59.94. However, it will probably have to be converted to a progressive format before being streamed.
I would still ultimately recommend 720p instead of 1080i if it was just an option between those two. Most software cannot handle the deinterlacing of 1080i signals well, and it is very common to get artifacts and the "window blind" effect (horizontal tearing during motion).