This is one location that access really counts. There will be maintenance needed on just about everything that is bolted to the motor. They fall into two categories, Maybe and for sure.
Maybe.... least likely first.. Sump. Accessory case. Cylinders.
For sure... Everything else. including.. Spark plugs, Oil filter, Sump screen, Air filter, Mags, Timing mags, Fuel pump, Rocker cover, intake, and exhaust gaskets. All oil and fuel lines, and all spark plug wires.
Think about how you are going to change an oil filter or change a mag. Keep the area clear of unneeded wires and hoses. The motor mount tubes are already in the way, use them for wire and hose runs.
If you are going to maintain your RV, you will thank yourself in the future. If you are sending your RV to a mechanic, his job is made easier, quicker... $$$ saved.
Plan your routing to avoid conflict. And for wire retainers, consider pull ties. They are cheap, simple to install, easy to maintain, and easy to update when a wire needs to be added. Be sure to trim the tail flush to avoid future cuts.
These two pictures are wired with 4 egt's and 4 cht's. Not one of the eight wires are in the way of anything except the sump... and it's least likely to be removed. And if it needs to, I just cut a few pull ties and the wires are removed.