It should work fine. The only disadvantage is that the boiler will need to continue to run throughout the year. Not familiar with that particular one, but many of them, when on, cycle between the max and min settings, so there would be some standby losses. An indirect is pretty efficient and that boiler is probably 2-3x bigger burner than a typical standalone waterheater, so it should work fine. Since these things have the wholel boiler to reheat water, you usually can end up with a smaller tank than with a standalone. The thing to check is the first hour delivery. Some of them are available with SS tanks, and should last essentially forever. Mine is a SuperStor Ultra. I can dump 40 gallons into a big tub and be doing wash and dishes at the same time. My boiler only has 80K BTU. The tank is insulated well enough so that the boiler only runs once or twice a day...but I'm the only one using it - more people, more use.
One thing that adds to the complexity is you should also install a tempering valve - it's required here, and a very important safety feature. So, figure that into your costs - plumbing it in adds to the complexity.