no, it will not overload the system. the only negative impact is delay & bcch/bsic planning :
delay:
it will take a bit more time for the BTS to transmit the list of all neighbors to the MS (you can imagine the consequences… not dramatic, but you introduce a small delay)
bcch planning:
don’t forget that you must avoid neighbors using same bcch. If you declare useless neighbors, it means you are artificially increasing the difficulty to reuse a bcch frequency… Knowing how complex can get a frequency planning, i would avoid wasting bcch at all cost !