I have the blind roller part on my office floor at the moment as I still have one door card to fit. I have been thinking the same and would say it’s ‘doable’, as the roller section can be dismantled.
You’d need to find blackout material that is the same thinckness as the netting, and be patient rebuilding the roller.
My short term fix is to make a blackout card that fits between the the blind and the window, reckon that’s good for occasional use.