Brilliant bit of DIY. The only observation I have is that a piece of soft foam rubber, inside the box where the bees will land, might prevent a few headaches for the bees. You might also want to think about some sort of extendable rod (landing net handle, etc.) to attach to the hose with elastic bands for when you want to operate it remotely e.g. when you don't want to climb into the narrow part of a roof-space or when you don't want to get down on the track - you could do it from the loft hatch or platform.
Is the inside of your suction pipe smooth or ribbed?
Will LU pay for this bit of kit or is it your bit of give, for taking the bees home?
CVB