That's a fair question. So long as the owner is still the defendant and the owner is charged with an actual crime, I don't have a problem with assets being 'imprisoned' similarly to people to prevent them disappearing during a trial in case they need to change hands in a judgment/sentence. However, they should not become the property of the state, which is what happens in civil forfeiture confiscations by default. An public or private escrow service seems like the most appropriate solution in your scenario.

If you allegedly rob a bunch of banks, and allegedly launder the money somehow in some vague unclear way according to a claim made by police, then yes absolutely good to go.

That's the cornerstone of a free society.

If they can prove you robbed the banks or laundered the money, then they get to lock you up.

But yes, in a thought experiment where someone commits the perfect unprovable crime that can't ever be solved then yes they get to go free.

The difficulty of proving something beyond a reasonable doubt does not justify the lowering of the standard.

It is up to the government to prove guilt. Someone shouldn't have to protect their assets from forfeiture by proving its innocence.