I absolutely would sign AI for the rest of the season. Not that he and Barbosa are identical players, but they both provide that energy off the bench and AI knows what it takes to succeed.
There is no guarantee that he will be amazing, but why not give him a shot. When he was terrible during his last stint in the NBA, he wasn't playing for a top-flight franchise like the Celtics. I think he would take his opportunity with us very seriously.
And I couldn't care less that he wouldn't play in the D-League. Frankly, he is above it and he shouldn't waste his body playing there when he doesn't need to.