I know, and it's not your imagination at all, there are real reasons why you don't see 250-lb people at Wimbledon or Forest Hills or anything like that and I've never even thought about playing serious tennis.
Nonetheless, over a long period of time, I've had friends and room mates who did and at one time I'd gotten good enough to give those guys a serious workout hitting groundstrokes.
Aside from everything else, I'd developed an unorthodox one handed backhand which was significantly more efficient than the shot which is normally taught and which was a murderously hard shot and for all of that, fairly easy to control. This is not a weightlifter's shot or anything like that and certainly anybody strong enough to play high level amateur tennis or professional tennis could hit this shot without any danger to life or limb.
The unorthodox inside-out backhand uses a totally normal backhand grip with the weight of the hand over the top of the racquet handle. The explanations of grips I've seen on youtube leave a bit more than I'd like to the imagination; this is my own shot at such an explanation:
Naturally enough as you can see, this shot assumes you have the ball in a certain hitting zone and that you want power. You're still going to have to be able to slice shoulder height backhands and you may still want to be able to slice low backhands which you want to skid or run out.
Basically, at any level of tennis, there are three things which are difficult to do and which are relatively rare, and any of which is a significant advantage to the player who has it: any sort of a hard and controlable serve; volleying; and any sort of a weapon backhand. The weapon backhand to my knowledge is the most problematic of the three.
The closest analogy which comes to mind easily for doing anything like this would be what is called "arm punching" in boxing. You can tell the arm-puncher easily enough in prize fights: he's invariably the person being carried out in a wheel barrow.