UPDATE: Since the last maintenance, closing NGS will get you kicked after some time.
I have got 3 Mabi's running simultaneously and logged in with NGS active. None of them were kicked out (Duration 1 day until I shutdown my computer).
Uhm... But I had it always running and until now no problems.
As for disabling data folder, gonna try it. For now was trying out using just a custom package, and that seems to be fine.
Update:
Got kicked with Abyss, DataFolder=0 and custom pack (yup, deleted the data folder too).
Gonna try running with just the pack for now.
Update2:
Have been running clean Mabi with just a custom pack for a while without problems.
Launched another instance, played for almost 3h with Abyss and even Morrighan and didn't get kicked.
For that note... Those 2 NGS packets are a bit odd... The data that client sends look kind of like random dumps from game's memory.