For me this seems to be reasonable and sounds like a very good idea, because it would then not take not necessary further space of the main window and because in the PROPERTIES context Sidebar is a lot of unused space.

Steps to Reproduce:
1. Open IMPRESS
2. Go to INSERT -> MOVIE AND SOUND and insert a sound or video file
3. (Optional if you had never activated the Media Playback in the past) Go to VIEW -> TOOLSBARS -> Select the MEDIA PLAYBACK toolbar 
4. Click on the media file

Result: The Media Playback toolbar appears in an extra line at the bottom.  Here you can now start the file, stop it, wind it forward etc. 
Now take a look at the Sidebar on the right.  In PROPERTIES section of the Sidebar you have only the Position and Size values and a lot of unused space below. 


Reproducible with LO 4.3.4.1 (Win 8.1).


@Jay: Do you have the same further issues as I?  
I have no tooltips for the Wind Forwards and Volume controllers.
The buttons in Media Playback toolbar could be a little bit darker or have a higher contrast (in case of SIFR, CRYSTAL and TANGO icon style).  The SIFR, CRYSTAL and TANGO icon style have all the same buttons.
Does the Scale View drop-down list box have any effect for you?

(In reply to A (Andy) from comment #1)
> @Jay: Do you have the same further issues as I?  
> I have no tooltips for the Wind Forwards and Volume controllers.

Yes there aint tooltips for it, you should file that one. CC me if you want me to confirm it. :D

> The buttons in Media Playback toolbar could be a little bit darker or have a
> higher contrast (in case of SIFR, CRYSTAL and TANGO icon style).  The SIFR,
> CRYSTAL and TANGO icon style have all the same buttons.

Yes the gradient on the stroke is causing it not to look that crisp. Yes they are all falling back on the tango icons.

> Does the Scale View drop-down list box have any effect for you?

No it is disabled for me and the tooltip just says 'View' which i was wondering what that was supposed to mean.