Scale, as the members are writing, Grady does equip smaller boats with a Sanipottie but the model has the pump-out withdrawal tube and fitting - built in, so the base stays put and the upper portion holds the flush water as usual. 5 gallon base make it a few inches taller than 2.5 gallon base and can go longer between pump-outs.
The Sanipottie has a bellows hand pump no electric needed.
Then inside the boat the 1.5 inch hose coming out of the sanipottie in your case would go to a deck fitting for the pump out, mine is in the walkaround floor. And yes, vent fitting is needed thru the hull side (5/8 inch).
Normal factory equipped Sanipottie system has a Selector Y valve with one side going to deck pump out, the other going to macerator pump with the 3/4 inch outlet hose leaving the boat via a thru hull out the bottom of the hull, for use more than 3 miles off shore - at least off the Atlantic shore where I am.
If you don't put the deck fitting in for pump out, I guess you can keep short or coiled and and bring in the facility hose into the cabin.
You really don't need the vent line if you remember to keep the flush valve open when pumping out, otherwise I imagine what's going to happen to the waste tank when it starts to be sucked and collapses.
For nicer toilets made of porcelain like at home - called marine heads and step up to a vacuflush system - require must more space for the larger components, you then do need the larger boat like a Gulfstream or Islander. In addition to the toilet, I have a 14 gallon holding tank, macerator pump, pressurized FW feed from the ship's FW system, vacuum generator storage tank unit. At more style, one pays more for the system. The cost of the level detector for the waste tank, or macerator pump alone, is more than the entire sanipottie.