I have long wanted to see a Rishi or an Odessen Stronghold.
Odessen could either be a smaller single floor layout with a starship hook or a traditionally larger layout set in the mountains. The smaller layout could be set via access through the cantina or a lit similar how the wilds were accessed or how the PC's ship is accessed from the military hangar. In terms of access, it could just be a reward token (plus credit cost?) for any PC who has completed KOTFE/KOTET at rank 10/20 influence with Hylo Viz, Sana Rae, Beywan Aygo, and Dr. Ogurobb. Also possible for anyone who has completed the storyline expansions with 'X' number of characters or 'X' number of times.
Rishi would be an amazing place for a Mandalorian/Smuggler themed Stronghold. Again, either a smaller apartment-type layout on the main area or a larger island retreat, perhaps taking inspiration from Torch's Mandalorian compound in the Blood Hunt Flashpoint. As for a way to unlock, completing the Rishi (possibly Yavin as well) storyline would necessary. I liked how the Umbara Train was purchasable with a certain number of research data packets, perhaps something similar could be used to unlock the Rishi Stronghold. Either by completing Blood Hunt a certain number of times or via separate mission chain from Shae Vizla - eliminating an uppity group of pirates or slavers that had taken over an adjacent island in her absence maybe?