I think everyone knows the fan base is still there without the need to actively call for people to turn out. I think too many instructions and caveats will distort the message. Let's call for just one boycott at one match, initially.
There was 26-27k home fans at the East Lancashire derby last year, we took 5k to Preston this year, 6k to Sheff United for the FA Cup quarter final, 6k to Anfield about a decade ago, 5k to Doncaster on a midweek for promotion. 26k on against Oxford in L1. I've no doubt that if we had somehow made our way into the playoffs there would be 30k fans after a Wembley ticket. When there is a huge fixture even many of those who stay away are temporarily drawn back in with their fingers crossed that things will change (they won't under Venkys). I'm not worried about demonstrating we still have an active fanbase. There's plenty of evidence.
I'm one of the few still attending and I'm briefly prepared to stop to send a message. We need to think about how we communicate/convince/plead with the other remaining attendees to make a stand. Just for one game.