I have a little question and i hope you can help!

We have installed Directadmin on a Debian 8 server that was running on a VMWare hypervisor. All was well, but we have switched later on to KVM. (Proxmox)
We have chosen to migrate the server with rsync. (install a clean debian 8, rsync / (with exceptions of proc, fstab etc...)) The migration worked like a charm with a downtime of about 1 hour (300 domains)

But we did forget about one little thing....... By excluding fstab we did not enable quotas on the new server, so all the users have a hugh amount of space at the moment.....

By adding the quota to fstab and rebooting the server will there be no consequences?
I would guess that users that are over quota they will be suspended.
But i was wondering will the system accept al the quotas? Or will we need to update all client profiles again so that the quotas will be saved? and because the configuration has been copyed over will the OS find it any fun or will we get a hugh amount of downtime?

I hope you can help me find a bearing what kind of things i need to take into account or test before enabling quotas on the file system again.