There are two ways I’ve seen the transport played
Keep BB and original transport by Italy along with the purchased transport which makes for a moderate sized Navy. Assuming success with the Luftwafe/sub attacks taking out the UK Med fleet, the UK won’t have much with which to attack this fleet, maybe 1 sub, 1 bomber? The US to follow up with 1 bomber? Unless I’m forgetting something this isn’t real good odds for the UK/US, although I can see it being attempted as its not great for Germany either.
Keep the bought transport at Italy (of course, its the only option for placement) and the original BB and transport near Egypt. The UK won’t be able to attack both with great odds, maybe bomber against the Italy transport and 1 fighter against the BB and original transport. The UK sub should have easily been sunk with the BB and perhaps a fighter although there is the chance of a hit by the sub in defense. If Russia attacks, they could lose a valuable fighter that they need to help strafe Japan later in the game and to help hold Karelia.
Either way, this most likely extends the life of the Germany Navy in the Med by at least one turn. In a no-bid game, this might enable Germany to move a couple additional inf to Africa which will be crucial for any chance for victory, the 8 ipcs will be more than recovered by either a longer span in holding Africa, or by forcing the Allies to retake Africa strong, thereby weakening the reinforcement to Karelia.
In a bid game, this could enable the German Navy to escape into the Indian ocean which opens up different options (Madagascar, India?, Australia?, New Zealand, or how about Brazil with the bonus of the German navy in S. Atlantic to prevent shipment of troops to S. Africa by transport?). While this is somewhat duplication of what Japan could do, it could force the Allies to react to a situation they have not seen before.