This project could be good thing for Bangladesh at the end.
Sure China will not withdraw total water. This project will force indian belligerent and water hegemony imposed on Bangladesh for last 45 years to an end.
With China holding the gate, india will be forced to agree to terms and terms could be -
1) Bangladesh and india will get certain percentage (100-X%) of total water GIVEN during lean season Bangladesh gets greater than 65% of (100-X%) water 5 KM inside Bangladesh border.
2) Water release of present year will be conditioned upon indian water release record to Bangladesh on IMMEDIATE PAST YEAR LEAN season.
3) NO other river flow in indian territory is allowed to drain into Brahmaputra river.
4) NO dam or diversion can be build in india part of Brahmaputra river.
and more ......