definately not. By by not indicating left (or right!) before exit B shows my intention to remain on the island. A right signal is superfluous.
No such thing as a signal to stay on a roundabout. signals should be clear for other road users to understand and you can’t make up your own rules - we all should work with the same code of practice. Not good practice to use a signal to stop the progress of other road users. Look early take your possition in good time and you will have no problems.