@CyanI think adding some of the core Ultimate Backup and Stop The Ped features to LSPDFR would be a good idea. I think that result of the way the plugins have been managed, and now not updated for over a year, dependency on UB and STP isn't good.
I think the most important features that should be a part of LSPDFR are having backup stick around a scene until you're finished, having some basic form of ped interaction menu and having an LSPDFR equivalent of the STP context menu.
With having backup stick around, obviously there should be a way to dismiss individual units or all the units, but I think that the LSPDFR team would be able to come up with some good ideas for how backup should respond to the player and the situation while on scene, basically having backup responding more dynamically to their environment, and not just standing there and copying the player's every move. As regards backup, I also agree with @Deputy kei's suggestion for ambient and backup K9 units.
Secondly, with a basic form of ped interaction menu, I envisage all the features that base LSPDFR allows when interacting with a ped to just be incorporated into a simple menu. I don't think that having every last feature that STP offers be incorporated into base LSPDFR is necessary, I think that an API (or something, idk code) that easily allows the community to add different features to this menu would be a better idea.
Thirdly, I think an LSPDFR equivalent of the context menu (i.e. a scene menu) would be a good idea, if you were to incorporate key UB/ STP features into LSPDFR. It could possibly even be under the same keybind as the ped interaction menu, with a selection at the top for 'Ped Interaction' or 'Scene'. Key features of such a menu would be the ability to call a towtruck and call a coroner. It would be good as well to have any service be able to be customised in a data file. Again, I think that including the minimum amount of features that is necessary for decent gameplay would be enough, with the community being able to add extra features that they would like to see.
Finally, thank you to the all LSPDFR team for all your hard work developing LSPDFR and keeping it up to date, and maintaining this website. Thank you also for taking the time to read my message!