Based on my experience, I dont believe there is a huge demand for blend. Most just parallel it in the DAW. You won't have to populate it or use it.
HPF - extremely common and useful feature, especially the filter posted by Magnus, which I included. You dont have to populate or use it.
Only reason I mentioned blend is because I still do plenty of mixing out-of-the-box / on a console. Also Pro Tools doesn't always play nice when trying to do parallel processing via hardware inserts
Glad it is being implemented this project is very nice.