One thing you can be sure of is that somebody had to connect that hose to the outlet from the pump in the first place, so there must be access to it sufficient to enable the existing hose to be removed and exchanged and for periodic maintenance. You say there is a floor hatch, so open it and check what can be accessed through it, you might find that it's not so difficult after all. You don't need to get your head through it, just your arm, so have a good grope around to find what you are after. Otherwise it may mean lifting the whole toilet. You have also mentioned lifting the floorboard, so ask yourself if there is provision already there to enable that floorboard to be lifted. If there is provision then lift it, but if there is none then leave it alone. Lastly, is it possible that access is provided from an adjoining space?
Once you have found the access point, keep in mind that removing a hose from a fitting can be a whole lot easier with very careful use of a heat gun. Do remember though that great care is needed with a heat gun, you don't want to melt any plastics or start a fire.
