Does such an option exist in Imp1? I can't find it neither in manual nor in game.

Cargo ships never become obsolete and have no upkeep so there's no tactical reason to disband them

You can let the warships fight until they sink

Oh, of course I meant warships, sorry for omission. I was just pondering about the idea of disbanding some of them for alleviating my upkeep burden without declaring war to anyone.