This would be great! You can mass update cross sections and bank line elevations, but to update the river reach it's a lengthy process that requires navigating through the menu at least 4 times for each one:
1. Select the river reach
2. Model->River Reach->Build Sections from lines
3. Select the bank lines (plus an extra couple clicks from the multiple selection dialogue for each bank line)
4. Model->River Reach->Build Banks from Selected Lines
5. Model->River Reach->Build Boundary from Banks and Section Ends
6. Model->River Reach->Build Bank Connections
You should be able to streamline this process and have a way to link sections and bank lines to their respective river reach so you can update multiple river reaches at a single time.
