As with anything, all of these can be done via plugins, and this is often as good a way as there is. However, in each case it means adding plugins in the signal chain… enhancing the existing functionality in each case would simplify the signal chain (always good).
Bitmeter: — specifically looking at having an indicator of inter-sample clipping, which I am not sure the level meter provides - ideally one that counts how many times it has occurred since “resetting” the count (one inter-sample clip over a whole song is not worth worrying about, multiple over a section of a song indicate an issue)… it is very easy to miss them if you only have a indicator flash when it happens - especially if you are watching multiple things at the same time. Currently using schwa’s “Bitter” plugin to do this but would be nice if just in the box.
Level Meter: — this is more about having the option for an analogue style display, which can be easier to work with when monitoring multiple things at the same time. Currently I am using plugins to do this (of which there are plenty including PSP TripleMeter or Klanghelm VUMT) but, like above, this does mean even more plugins in the signal chain.
Loudness: — probably not explained this one well enough so maybe easier to point at an example of what I mean, which is the YouLean Loudness Meter which provides a really great history graph over time of the LUFS against the targets - again making the monitoring of this easier when you have multiple meters showing. The histogram does not seem to do the same as this (although I might be misinterpreting it) and audio file view is not a LUFS view!