you need to understand 1 thing about fastbreaking, when i had Satellite Internet with 5k ms ping to server and i used a Good(eff 5) tool, it would say i was fast breaking because on the crappy internet i "Had" it would send chunks of info during lag spikes, which would trigger the server's anti-fastbreaking. and also when going down ladders it would kick me for flying whenever my net had a lag spike. So if you want to lose a few people from the server who might be on crappy internet and playing legit, then go ahead and punish them with it, i stopped playing on a server awhile back when I had my old internet, now its faster and don't run into this issue. Ever. Keep in mind, you need to look at all angles of this topic your trying to ask to be implemented and think of its logic.
^my internet is crappy but whenever I go thru a lag spike while melon farming I either lag thru a bunch of broken melons or I get kicked for commection timing out. I have gotten kicked for breaking blocks out of sync like 3 times and they were all during lag spikes, you have valid points and invalid points.
As far as I know, 'upper-class' Staff Members (GameAdmins, Server Admins) check personally on potential felons to make 100% sure they are really Fast-Breaking before banning them, so I don't think bad Internet Connections would really cause any troubles to players other than the occasional 'Block Breaking out of sync' server kick.
yeah, for short bursts this can probably happen. but if it is happening for a long period of time, the person is using a hack.