I have been through this myself with another "dominant" I had once.
For me like others it just wasn't the same after, he totally lost any control over me in the relationship.
There is nothing wrong with people wanting to switch roles, just don't expect everyone involved to be cool with the idea, especially if the relationship is allready well developed along D/s lines with clearly defined levels of dominance and submission.
We even talked about it before hand, I expressed my conserns that it would alter or relationship forever and yet after some pressure from him I relented to his wishes becuase I so wanted to please him. (he wanted me to use a strap on with him and play at being a domme, which much to his later chagrin I did so with every bit of intensity I could muster).
He also used the same logical argument that it shouldnt in any way be detrimental to his position as a dominant, I did my best to conform to this line of reasoning but human emotions however are not allways logical.
I tried my best but the bad taste it left in my mouth never went away. I was never able to see him in the same light again, let alone submit to his will. Our relationship continued for some time despite my feeling trapped and recentful with the new arrangment .
It was a very unfortunate way to find out that we were incompatable.
Nieather of us was very surprised when I was very easily wisked away by a much older and more experienced dominant that could tell instantly what was wrong and that I was so very unhappy with the role revesal.
However one must be true to one's self. If you really feel like switching roles is the thing for you, it wont be doing yourself or your submissive any real favors to hide from it.
It may be a painful way to find out what is true for your own nature as well as your partner, but growing and learning to understand one's self as you make your way in the world is not allways a pleasurable experience.
I wish you the best of luck.