Question when you say cable support where is that needed. We are running new lines from bilge through a chase tube into console. Are you saying the cables should be supported before entering the chase tube or coming out of the chase tube before they connect to the batteries or both?Just let them know how you want it done, Where you want the Switch and batteries located, orientation, proper marine cable (and lugs) routing and to use proper cable supports. Not zipties. Lots of "marine techs" take the fastest/shortest route.
A job done well with the proper materials goes a long way.