How dirty? don't know yet but it's very likely that after 10 years even if filled with diesel only from car filling stations + anti bug additives crud will stick to anything inside.
Always wondered how and why a professional yacht building company as Bavaria would be so ignorant/careless about owners needs to maintenance!
-No inspection window on a fuel tank.
-No option to remove the fuel and water tanks for cleaning or repairs.
-No draining option from bottom of fuel tank or oil from engine .
-Using cheap not seaworthy brass seacocks.
-Crappy electric swim platform.
And some more...
Sounds like you need to buy another boat.
Access to the fuel tank is adequate. The deepest part is at the front and easily accessible to extract any crud.
Plastic tanks are far more reliable and stay clean better than metal tanks so the need for removal is rare. BTW have you ever tried to remove the mild steel tanks on that high quality UK brand - Moody? or deal with failing built in GRP tanks as commonly used a few years ago by many builders including HR?
Very few boats have drain points simply because the flat bottom designs do not allow room. Top pick up is almost universal. You fuel tank would have to be on top of your berth, or thee sump and drain exterior to the hull to be able to fit a drain.
An oil extraction point is provided on the engine. Again very few boats have room underneath to access a drain point here - for the same reason as no drain on the tank.
The use of brass seacocks has been the norm for many, many years in Europe (including high cost builders like HR). Given the literally hundreds of thousands in use there does not seem to be an epidemic of failures!
Agree about the electric platform. Big mistake, quickly dropped and the latest type is a model of simplicity and reliability.