My 2 Cents
I agree with John: sail for a season and see what you really need. When I bought my Oday 23, she didn't have a depth guage or a working knotmeter, only a very outdated Magellan hand held GPS. I found that even in LIS where I sail, I have been able to do without a depth gauge very nicely (although I am always thinking of adding one). I never fixed the knotmeter, but I did upgrade the GPS when the Magellan finally crapped out. I went with a second hand Garmin (eBay) that has all of the buoy locations pre-loaded, but can't show charts. Is a full-on chart plotter too much for an Oday 22? It may not be necessary given the type of sailing you describe, but hey, if its a toy you want that increases your fun factor, then I say go for it. I think you have found that if you want something than function as a chart plotter and that you can take in your car, you will not be able to find something that will also serve as a depth guage.