This is a very specific request, but what comes to mind is not a plugin but the S2400 sampler by @islainstruments - you can let the sequencer run, enter notes and if they're not right, delete them by holding delete and the pad your sound is on, so per channel, not the whole pattern. You can do this to your heart's content. It's an AMAZING sampler. That's just one (and the least of the most impressive) reason why it's my number 1 favorite pieces of gear... ever really....