Is it possible to generalize HR diagram to include planetary nebula to (near?) black hole and IR emitting sub-brown dwarf to X-ray binaries, if peak of blackbody spectrum (or other suitable parameters) are used instead of color temperature, and some sort of normalized blackbody-equivalent power output instead of visible (absolute ) magnitude is considered?
Not in a useful way. The 'odd' systems you are considering are too variable in their characteristics to be treated with the same simple comparison represented by the H-R Diagram. Normal stars (even red dwarfs and brown dwarfs) have to have a particular mass and be in a particular stage of their life to be in a particular place on the H-R Diagram, so it is an extremely useful tool for studying stars, especially stars in clusters, where their difference in distance from us is small compared to their average distance. There are ways of comparing other objects, but they are difficult, different for every type of object, and not always reliable; and in any case, they are not at all like the H-R Diagram.
I concur with Courtney Seligman. The HR diagram is about a mass/temperature/luminosity relationship. I don't think that we can use that same relationship in the context that you are describing.
Nobody will forbid you to plot your preferred bodies in a kind of HR diagram. But to make sense the plotted quantities should exist in theory, or be measurable for observations.
The abscissa should represent the body "surface" temperature (in log), it means that temperature is well defined, that is there is a kind of photosphere where photons escape but an approximate local thermodynamical equilibrium still exists.
The ordinate should represent the radiative energy output, a power (in log), that is some radiation should be emitted.
Planetary nebulae are very transparent, so the notion of photosphere does not exist. For these "bodies" the HR diagram does not make sense.
Classical black-holes do not radiate, so they have no well defined temperature, and no energy output. If Hawking's radiation exists (still to be proven) one could eventually use its equivalent temperature and power to put black-holes in a HR diagram.
Brown dwarfs or planets do have a well defined temperature and IR radiative energy output.
The X-ray emission of X-ray binaries comes from the mass transferred between two stars so for these objects the HR diagram using the X-ray emission is not suited.
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