When looking at the progression of the Pokémon series, there are some clear patterns in how games are released. Nintendo typically has been releasing remakes of older titles every couple generations. For example, Gen 3 saw Fire Red and Leaf Green, Gen 4 saw HeartGold and SoulSilver, and Gen 6 saw Omega Ruby and Alpha Sapphire. It's about time for GameFreak to release a new remake and, logically, that would mean it's time to revisit Sinnoh in Diamond and Pearl.
However, GameFreak also has a tendency to cut features at random. This includes features that people actually enjoy, like Pokemon followers or the Battle Frontier. So, in the jump between Sword and Shield and potential remakes, some features have to go. This list will provide some features that GameFreak should keep, along with features that are better left not being iterated on.
10 Do Keep: Pokémon Camp
While most people would see this as a fairly unimportant feature, Pokémon Camp is fun. For trainers who like building their own story, Camp was basically just Amie but better. It's form in Sword and Shield is fairly simple, but that doesn't mean they can't spruce it up. GameFreak could include new toys to play with or mini-games, such to start. They could even use the Camp as a better justification for 3D games. This is a fun little feature, and it would be a shame to not let it make a return.
9 Don't Keep: The Wild Area
The Wild Area is Sword and Shield's defining feature, even more so than Dynamax. It's the most unique thing the game delivers and loaded with secrets. However, if they were to cram it into Diamond and Pearl, some of the magic would be lost. It would be smarter for GameFreak to build a title around the Wild Area than just shove it into a remake. For the sake of the framerates, wait until a new title to take another crack at the Wild Area.
8 Do Keep: Title Defense
This feature was added in Sun and Moon as a way to make Elite Four rematches more exciting. GameFreak further expanded on this concept with the Champion's Cup rematches, which allowed the player to customize the bracket and challenge.
With another set of iteration and Diamond and Pearl's cast of characters, this Title Defense mode could become something very interesting in the post-game. If they decide to make it a challenge that requires competitively viable Pokémon, that would just be icing on the cake.
7 Don't Keep: The Battle Tower
The Battle Tower has been a staple of the Pokémon series for a long time now. It evolved from being one-part of an extensive Battle Frontier to being the main attraction of the post-game. And, quite frankly, it's about time to change things up. Being stuck with an underwhelming Tower at the end of every game just feels bad, especially when looking back at what trainers used to have. Either bring back the full Battle Frontier, or add a bunch of new competitive modes to the Battle Tower.
6 Do Keep: Toby Fox Arrangements
Sword and Shield has some incredible music. One of the best songs in the game, however, wasn't even composed by GameFreak's main team. The Battle Tower's theme is composed by Toby Fox, creator of Undertale and the infinitely memetic (but still fantastic) Megalovania. Toby Fox is an incredible composer, and giving him the ability to arrange some pieces of Diamond and Pearl's soundtrack would add some spice to the overall package. It would be a joy to see what Toby could do with both battle music and route themes, like the iconic Route 209.
5 Don't Keep: Dynamax/Gigantamax
Despite some cool designs, many players found Dynamax to be an underwhelming new addition to the game. It was an improvement from Z-Moves, but that's not an accomplishment. Balance aside, Mega Evolutions were more interesting in casual and competitive play. Aside from that, from a lore perspective it wouldn't make sense to include Dynamax in Diamond and Pearl remakes. This would mean the actually cool Raid Battles can't return, but that's a small price to pay. It would make more sense to return to Mega Evolutions or, possibly, just ditch the gimmicks outright.
4 Do Keep: Post-Game Story
Post-game stories have been a major part of the Pokémon series going as far back as Gold and Silver. It's easy to laugh about Pokémon canon, but it matters. As the games got bigger, their narratives attempted to expand as well. Sword and Shield's post-game story can generously be called "an attempt". However, this doesn't mean the concept should be scrapped outright, even in DLC.
If GameFreak focuses on further developing characters that people actually like, that's a great first step. Sordbert and Shielbert may be terrible, but GameFreak can easily make a post-game narrative that's rewarding to finish.
3 Don't Keep: The Y-Comm (In Its Current Form)
GameFreak has been iterating for a long-time on the best way to handle online features. Every game since Pokémon X & Y has fundamentally had identical online features. These features have been one of many problems with the series. However, Sword and Shield outright made things worse for no reason. The inability to directly connect with friends, instead going through a three-digit code that can be sniped, is frustrating. GameFreak should focus on making online play less of a burden, even if Nintendo platforms are famous for bad online.
2 Do Keep: Competitive Battling Ease-Of-Access
It's clear when watching recent VGC games that the competitive series has expanded tremendously. Part of that can be attributed by how many tools GameFreak has given players to make getting competitively viable Pokémon easier. Gambling on natures and abilities are a thing of the past, thankfully. This isn't a bad thing by any stretch of the imagination, and reducing the grind is a blessing. Nature Mints were a blessing from the heavens, for example. This direction is one they should continue to pursue.
1 Don't Keep: Limited Number of Pokémon
A regional Dex having a limited number of Pokémon is understandable. In fact, cutting out some Pokémon people weren't going to use anyways isn't even a bad idea. However, not giving players the option to use these Pokémon at all ends up just feeling bad. Some players have fun using Garchomp every game, and that's a valid way to play. There are understandable limitations in the hardware, but once these models are created, just start reusing them. Trainers only care that they get to use Chikorita, not that Chikorita looks exactly the same as it did in a previous game. The only Pokémon that deserves to be cut is Charizard.