There are two questions here:
1) what is the minimal equipment for indoor swimming photography
2) what equipment will you really want to bring to a indoor swimming meet.
Large aperture lense give more light to the camera sensor to give the command to the motor on camera or lenses to do the actual focusing. Low end equipments have less light, slow motor and poor sensor.
The D4/D3s are the best sport bodies (Nikon family) for sport, and the 70-200mm/ 220/328/428 are the best lense. Even so 70-200mm is @ F2.8, it is developed for sports. It focus a lot faster than the 85mm 1.4G, for example.
After focusing speed, then there is FPS and the response time. From the time you press the shutter to the picture taken. Most low end equipment will miss the shot.
For Q2. The indoor swimming meet are hot and humid. The humidity is at least 90%. I would not take my best equipment in there unless I have way to dry them during and after. If someone wanted to borrow my 328 to an indoor swimming match, I would refuse.
Shotting indoor sport is one of the most equiment challenging area. Indoor swming is almost impossible.
