In regards to it needing a transport to move it on the sea: I see it as a way so it’s not just a free movement across the sea as you have to invest in transports to move it accross. Otherwise you might as well just hand it over the IPC’s to UK, perhaps with a delay. Which would just make a gamebreaking strategy of USA giving all it’s money to UK making a unhistorical gamebreaking strat. Giving it a defensive value would in my opinion just make a strat of investing in cargo as cheap hit takers for the navy. Plus, theres a simple elegence to the two unit staking currently on the trans (1 inf 1 cargo).
In regards to it being defenseless: Almost all USA strat’s involve at least sending some “defenseless” transports to UK (E Canada shuck). In almost all the games I play Germany never has the ability to threaten them much as the risk rewards are high (Bombers are the only unit with the range, and only from Norway no less). Granted if you wanted to send a crap ton of cargo to UK, I could see a smart German player bombing those trans.
In regards to it taking to long: It takes just as long to send ground forces into the UK as it would to send the cargo. The cargo wouldn’t be a instant gratification unit, it would be part of a long term strategy to help bolster a quickly deteriating UK.
The other place I see cargo actualy being done is with Germany giving cargo to Italy. Germany doesn’t have to buy transports but there is a two turn delay and Germany can’t afford to give too much.
Additionaly, It could possibly be done with Japan giving to Italy (4 turns on the sea), or USA to Russia in the example I gave at the start of the thread. You could even spend the entire game trying to get a cargo to the Russian front with Germany.