Does Antonio rather like the idea of sacrificing himself for Bassanio's happiness?
I must say I rather like this question and there may indeed be something in your suggestion. The problem with Antonio is always that we don't know him sufficiently well to come to any sure conclusions about what drives him into his ill-advised bond. The great friendship that exists between him and Bassanio would surely have been tested to the limit by Bassanio's previous borrowing but no, here is Antonio again prepared to hazard a huge amount for someone he must surely see is a bit of a waster. Some productions of the play attempt to get around this problem by making Antonio an elderly gay man and Bassanio and his companions attractively young and fun men about town. I don't know of any that have tried to display a more explicitly homoerotic relationship between them, which I'm glad of because there is no real evidence for it. However, having Antonio attracted to Bassanio in an aching but unrequited way does certainly help to explain hs recklessness with the bond and could also support your suggestion that he finds some satisfaction in the self-sacrifice. Good thinking!