Having to add a channel group for alot of channels is a pain in the ass it would be easier just to hand out a server group.
Well, of course, if you have a lot of channels that's really a pain. But doing this with a lot of channels like you suggested, it's a very dirty workaround, because you need virtual jump channels for every channel of it.
A better suggestion is to have a bot chat command that assign the channel groups to every specified channel. So the client don't have to be online and you don't have to switch the client around. What do you think about the following chat command:
!setchannelgroups <client database id> <channel group id> <channel list separated with a comma>
As an example:
!setchannelgroups 42 7 3,6,8,24,45,65
This set the channel group 7 (which is something like the channel group Channel Access from my last forum post) to the client 42 in the following channels: 3,6,8,24,45,65
You can save that command in a text file on your desktop, just copy & paste it to the bot, just change the client database id, done. What do you think?