You say you want “simplier” but you already have simplier! We’ve always used a dipstick and find it handy enough and accurate enough. I used a Dremmel tool to scribe the numbers on an ironbark stick every 5 gallons. I probably check it once a month during our 3+ month summer cruise.
If I was having a new tank built, I’d like a way to drain out any water that accumulates at the bottom. I’d also like access ports installed. Our 34 year old tank is still going strong, knock on wood. I pump out the bottom fuel and run it through a Racor filter once a year or so, and that seems to have helped control the gunk that grows in the tank.
But I think I’d use a dip stick to check fuel level in the new tank. What could be simplier for a 28’ sailing vessel?