Not a good idea at all -- can cause undue stress to feet, ankles and parts of the legs. Ankle weights should not be used for walking, running or jumping. They are ok for doing other leg exercises.
Not sure that the wrist weights should be used when swinging a racket either -- especially when hitting tennis balls. This can result in too much stress to the arm if done too much. Also, you could actually be training your muscles to move slower, not faster. In previous threads I've posted a link to an episode of Sport Science (ESPN) that dealt with this type of overload training. Their conclusion was that the thinking behind this type of training is somewhat fallacious. The muscles are actually trained to move slower. Timing can also be thrown off and stroke mechanics can also be altered if the weight is even 20% greater than the normally swinging weight.
You might try Overload-Underload (OU) training instead. However, this might not be easy to implement. OU training employs 3 phases. In the overload phase, you would swing a racket that is 10-15% heavier than your normal racket weight (or it might be better to use a racket that has a swingweight that is 10-15% greater). This would work on muscle strength.
For the underload phase, you would use a racket that is 10-15% lighter (or lower in swingweight) in order to train for faster swinging. You could use a racket without strings that is the same (swingweight) as your regular playing racket for this. Of course you could not hit balls with this unstrung racket. The 3rd phase is to go back to train with your regular racket in order to regain your timing.
