ABS and caliper rebuild?

Want to rebuild my front caliper at some point but I've got ABS. Can I just unscrew at the banjo bolt stick an earplug in it to stop dripping and finish the caliper off at my leisure or do I need to seal the thing up airtight or what? Most people who do brake line swaps seem to be bypassing the abs and blanking it off but I still want to keep it, just don't want to get air in it. 


I've done a couple of caliper swaps on the i20 and the Mini but that was literally old caliper off new caliper immediately screwed back on. 


Anything I have to look out for if I leave the caliper off for a day or two?