No wax makes things a lot easier, however, there may be a glazing compound in the top coat that will be difficult to adhere to. Cover the wall with a good Stain Blocking Paint (I am a fan of KilzMax by MasterChem ... I've seen CoverStain 1,2,3 recommended on here too though I've never used it personally).

A good Stain Blocker should deaden whatever is on your wall. I wouldn't tackle re-plastering yourself if you haven't done it before or practiced. If you like the "pattern" that is there now -- leave it alone. Your challenge will be how to create a new look with that professionally done under surface.

I would recommend a light tone on the whole wall covered fully. Then a deeper color (mixed with a glaze) that is ragged, sponged, or even large brush strokes randomly. This will dry slow due to the glazing compound but you can play with it for 30 minutes or so to get the look you want -- only do a 5x5' area at a time then repeat the process blending at you last patch.

For a really interesting look, do a light tone fully on the wall. Then a deeper tone randomly ragged or sponged. Then the final coat with a third color with the glazing compound. You lay down a smaller roller strip randomly (every foot or so) and then lightly brush that strip with criss-cross strokes or just rub it into the wall in circular motions.

Those are my ideas -- hope others chime in too,

It'll be a little tricky...
....but my 1st-choice is to lightly scuff-sand what's there. Remove ALL dust. Skim-trowel your new color on. Repeat as necessary to create desired opacity/profile of new color.

You may discover that leaving hints of previous coat may look nice!

Priming anew would be only a slight advantage, if any. Priming would lock you into covering any trace of it with your new VP-coat(s), when doing so MAY not be necessary.

I'm REALLY glad there's no wax on it!!!

Faron