It's interesting you mention that. FLUX just sent us all a Buildtak build plate as part of an upgrade kit for the original Delta to bring it to equivalency with the Delta+ But they took a different route, since the printer already has a metal build plate, they attached the Buildtak to a magnetic sheet that is about 2mm thick. When you want to print you slap the mag sheet on the plate and print, sticks like mad just like you both said, but then removing the print is super easy. Since it's a magnetic sheet, just take it off the plate and it can flex and the print pops right off.

In the case where you have Buildtak pre-applied and the bed doesn't come out easily or flex, another trick is to use a can of compressed air. The 'Air Dusters' that you find in Office Depot, Office Max, etc. for cleaning keyboards. The trick is to hold the can upside down and give the print a VERY QUICK spray at the base. The propellant used in those sprays evaporates and freezes at room temp, so that quick blast will super chill your part and make it a lot easier to remove.