Rejected I would like to suggest that both Terastallization and Dynamax should be allowed in custom battles.

[Poké Gamer Boy 17]

I know of a lot of people (including me) who were able to strategically use Dynamax to turn the tide of a battle, and while Terastallization can have a similar result, it's just not the same. For example, my best format is NDAG. I made it to over 1600 elo in the gen 8 format. So, when Gen 9 NDAG came out, I decided to try it out. I have struggled to get past 1300 elo. It's completely different, and I think we need Dynamax back in NDAG somehow. I've tried using some of the other formats, like Gen 8 AG, but some of the Pokémon I use aren't available in gen 8, like the Primals or Mega Rayquaza. I've thought for a while, and I think that the best way to bring back Dynamax in NDAG without disrupting any existing formats is to give players the option to use both Terastallization and Dynamax in custom battles. You could even go one step farther and make any of the 4 gimmicks available to use at any time (when applicable). However, if that would take too much work, I understand.

 

[Turtlek]

I’d support this in form of hidden clauses we could remove, /challenge gen9customgame @@@ !dynamax Clause would be awesome to have free to use

 

[DaWoblefet]

The only tier that even theoretically wanted to support both Dynamax and Terastallization simultaneously was National Dex, and it ultimately was not able to do so due to coding constraints. The main issue is that you can both Dynamax and Terastallize with any Pokemon, which means you have 2 simultaneous battle mechanics options needed every turn, which just isn't supported either server-side or in our user interface. Based on discussions about the identity of National Dex, it doesn't seem like that's going to change. Because of the difficulties surrounding implementation, and because no actual tier wants to have both simultaneously, I'll reject this.

 

[Poké Gamer Boy 17]

I have another idea to solve the problem I found that would be much simpler in terms of coding, so I'll post that on another thread.

EDIT: I appreciate you having a Bible verse in your signature

 

[Poké Gamer Boy 17]

I know it's been a while, but I just came up with a couple of ideas.
The first one is sort of like what Turtlek was thinking with hidden clauses. In one case, the battle would use Terastallization. In another, it would use Dynamax. Basically, either one or the other would be in play in any given battle, this depending on which clause is in play.
An alternative would be to make a custom battle format for each generation in which a new gimmick was released (ex. Gen 8 Custom Battle), so to reduce the complexity of the coding. However, this may clog the selection menu and potentially create more time-consuming work for the developers.
This would make it easier to bypass the coding restraints while still solving the problem I wanted to solve.