Staff will have to speak to whether any of the suggestions are possible, but basically none exist as-is, and I'm not aware of any easy workarounds for at least the first two items you mentioned.
For the third (enabling/disabling debug logging on devices), there is some hope: staff have teased that 2.2.5 will have an app that can automate the setting of preferences on any device. You could use this to turn on/off debug logging, for example. However, you would still have to select the device and the setting ("debug logging" isn't inherently part of this--just any device preference), plus some way to automate that (not sure they've disclosed exactly how that will work yet, but presumably you could either manually initiate it from the app UI or automate it with a virtual switch--we'll see). What it might help with is that you would no longer need to go into each device and do this manually. That being said, we've been told logging shouldn't really have an impact on app or driver code, so I wouldn't normally worry about this too much--but certainly logging only what you want is a good idea to make "Past Logs" more useful.
For log retention, I'm assuming you are already aware of "Past Logs." The live logs will hold things indefinitely as long as you keep the window/tab open, as far as I know (there may be a theoretical limit). Past Logs holds 256 KB of data unless that changed recently. However, I'm not sure if that is pruned in real time or as part of nightly or hourly maintenance (I think one of the latter). There is at least one third-party all that can connect to the logs "socket," which you could probably use to store that information elsewhere, but as far as I know, the hub itself doesn't--what you see is what there is. Limiting device and app logging is the best way to ensure that what you need is here...but I'm assuming you're aware of all of this and are asking for exactly that reason. 
