is it possible to load a transversal wave with a longitudinal wave
Yes it's possible and done in many applications, but probably not in the way you are thinking.  For all practical purposes EM waves are by definition transversal when in the far field plane wave mode and/or in free space which is illustrated below.  This is how a large majority of long distance communications operate.



This is not often the case in near-field applications or for Gaussian beam (laser) communications.  However this little fact doesn't mean you can also "load" them (we electron pushers prefer the term modulate) in a non-transverse way.  The E and H fields are all you have to work with so there's really nothing you can do.  Either you have TEM, TM or TE modes of propagation.

You can't really add information the way you are thinking...except, you can accelerate the source!  This will induce modulation in the form of a doppler shift.  You can then demodulate the doppler shift independently from the the data being transmitted.

But as far as I know that's about the only way you could do what I think you are asking in your question.  If I missed your point, then please clarify your question.