[IXRollOutIX]

Here's my theory.

So what if the "True" Gashat Riders are actually the Bugsters from the video games they're based on? It would explain why Dan has preserved Salty and Alanbura. And it would also explain why True Brave doesn't have a unique identity yet. For example:

Salty - True Mighty Action
Alanbura - True Taddle Quest
Revol - True Bang Bang Shooting
Motors - True Bakusou Bike
...etc, etc...

We see Bugsters that look like they come from Gekitotsu Robots and Jet Combat in the scans, so maybe they'll become Riders using those "True" Gashat as well once they're complete. And maybe Poppy will be brainwashed and forced to become the True DoReMiFa Beat Rider and Graphite will return briefly later on to become the True Dragon Knight Hunter Rider for a couple episodes as well.

Then once all 10 True Gashats are complete and their data has been collected, Dan will have what he needs to finish Kamen Rider Chronicle. And that's why it's called Kamen Rider Chronicle. It's defined by a new league of Bugster Riders. After all, Dan has said the original four were just tests subjects in the first place.