There is no problem at all to install a bilge pump in a SIB, in fact its a great idea (especially if pumping the bilge by hand gives you a hard time)
Have a look at the pictures, this installation was in a Milpro application in a RIB but it gives a good idea how it works. Most of the recent bilge pump has a built-in float switch so you just have to install the pump.
Like you can see on the picture, the blue plastic strainer (lower part of the pump) is removable, so by fixing it to the floor/bilge/transom/whereucan you'll just have to "click" the pump in place.
Electricty is quite easy too. If you have no electricity on board, you can use a small motorcycle 12 volts batterie inside a waterproof box (any electrical store have this) and put a breaker on the hot wire. For the switch, you have the choice between ON/OFF or ON/OFF/AUTO. On the 3 pos switch, you can put it auto so it primes when the float tells it to or manually overrun by putting it at ON. A good bilge pump should be self-priming and run-dry protected. In a previous project, we've installed the switch directly to the battery box, flush mount.
For the plumbing, you need hoses+scissors+tie-wrap. The bottom of the pump is the intake and you just have to run the hose overboard and thats it.
It is that easy!
Ok according to your lawyer profession you know that even an email advice has to be paid since it is a professionnal act, so how do you intend to pay me for my precious advices?