I wouldn't worry about being lazy but I would double vocals and bass with great care.
Re-using material within a song can add real strength to it, new things happen that sound familiar to the ear because we have heard them in another form already. It's a technique used throughout classical music and makes arrangements sound professional.
However, that said, having bits in the arrangement that double the vocal are dangerous. In general it is good to work in between the vocal melody, so you don't trample over it with other instruments, meaning the listener can't follow the vocal as easily.
So feel free to use the line but perhaps consider rewriting the baseline if you do.
Tom.