I've answered this question a number of times already. Read the Owner's Manual - Raritan toilets, by themselves, DO NOT retain water in the bowl between flushes. To have the toilet retain water is a function of the external plumbing. It requires that a vented loop fitting be installed, with the top of the vented loop situated higher than the top of the toilet bowl. That way, water will be retained in the bowl. As an extra-cost option, Raritan offers a built-in vented loop fitting inside the Atlantes head, that will insure that water is retained in the bowl between flushes. It can be included with the head when it is originally ordered, or is also available as an aftermarket part (Raritan part # AHDA1W). As it is a relatively expensive option, most boat builders do not include it in their new boats.
Because the toilets are built for a host of different applications, there is no set design that is suitable for all applications. If you have a sport fisherman and are going 80 miles out into the Baltimore Canyon on a regular basis for gamefish, as an example, you don't want water being retained in the toilet, as it will slosh out onto the floor when the boat is bouncing around in the waves. But if you have a houseboat that rarely leaves the dock, and is never in rough waters, then you do want water being retained in the bowl between flushes. Sorry to say, there's no "one size fits all."
I can't recommend modifying the toilet, or it's wiring, as you hinted - at least not until the warranty period has expired. If the toilets are not installed and operated in accordance with factory recommendations, warranty coverage will not be honored should a problem develop. To wet the bowl prior to the toilet being used, simply flush it once before sitting down...
