I mentioned this when the change was proposed - and it obviously got ignored.
I am not sure if anyone thought about this for long… But.
With the current change to GW Defense, we either need more Team Tabs, or a completely different system for setting Guild Wars defenses.
That’s all. Thank you for your attention.
I think, technically, you should be able to use just one team slot for GW defence, as long as you don’t mind updating the team every day.
The defence troops are locked at the start of the day. If you change that team during that day, it won’t change your defence for that day, but it will apply for the following days. And you should get bonus defence points based on what you had on that team at the start of GW day.
If my assumption is incorrect, somebody please correct me!
Also, yes please, more team slots! Even if I’m right, doing that daily would be tedious and it would be nice to avoid it. I actually have two teams for every GW day, so now I would want to have 18 teams dedicated to GW.
I believe that they stated the teams are locked on day 1.
Last week was not the case because it was implemented mid-week.
What!? Oh boy. I need 18 teams 
Pretty ridiculous. I know, right ?
… They might have probably only forgotten about mentioning this part of the change, where you’d have to lock the team only a day before …
But better not to take any chances.
A thrifty gamer might keep 6 slot occupied by locked-down Defence teams, and build a team-of-the-day at the beginning of each GW day.
It would lower the requirement down to 7 of 24 slots.
I have no clue if you have tp lock all days on day one or not.
So far it looks only 7 teams are needed, as you can lock the defense just the day before it starts.
… Which is still an irritating thing to do, as I constantly have to re-arrange it back every single time, double or triple checking, just to see it revert and set to a different one anyway.