Well, about the plumb the Rose. Besides the actual pump for pressurizing the tank water and the water heater, can I use household valves and toilets?
Not a good idea, not only for the reasons already posted, but because a) household toilets rely on a siphon started by releasing enough water from the reservoir (which has to fed with pressurized fresh water from your potable water supply or by a pump to bring in sea water) and gravity to get it to the sewer line, and...b) marine toilets are designed to PUSH bowl contents to their destination (tank, overboard, treatment device). You COULD use hard PVC for any long straight lines, but PEX and other fresh water plumbing isn't rated for sanitation or below-waterline use.
The flow path through most household toilets is 2", and some are up to 2-3/8". Marine toilets are usually 1-3/4", which may contribute to clogging problems.
1.5" ID is the standard size for discharge hoses on marine toilets.
Flushmate toilets use one gallon per full flush (I don't know if any offer a reduced flush for No. 1s). Marine toilets offer reduced water usage options, but this also contributes to clogs. I don't think one gallon per full flush is far off marine toilet full flushes.
Today's manual and electric marine toilets only need about .5 gal water/flush and when installed, operated and maintained according to mfr's instructions, rarely clog. 99% of clogs are caused by guests...the remaining 1% are caused by owners who don't maintain the system.
The RV toilets I have looked at have two concerns: as they don't hold any water in the bowl, odors from the tank can escape, and as they don't hold any water, many come with a spray nozzle to clean the bowl after use. Don't care for that.
Dometic/SeaLand RV toilets have flush mechanisms identical to their VacuFlush toilets...step on a pedal to open a trap door in the bottom of the bowl and start flush water running, lift the pedal to add water to the bowl ahead of use.
If you'd like some help designing a trouble-free ODOR free
marine sanitation system, give me a shout. Meanwhile, you might find some worthwhile information here:
http://www.amazon.com/New-Get-Rid-Boat-Odors/dp/1892399784/