Well first of all Trunks wouldn't be able to beat Aizen in no way can he not have his senses controlled, Trunks wouldn't even know if it was being used or not, For all Trunks knows he could use say.. Buster Cannon on his Mom or something ._. Like really He'd be completely mind ****ed by the whole entire thing. Aizen on the other hand wouldn't be able to survive a punch.. if it could actually land.. Which is a problem... Because Trunks has been shown to have a short temper like his father and Aizen's a manipulator.. soo.. Get ****ed Trunks. Besides.. If Aizen said Bankai.. Aizen Auto-Wins.. His Bankai probably makes the universe friggin implode I don't see Trunks doing that with his pansy ass sword.. Do you? Didn't think so -_- Oh.. Also.. if Trunks said anything Aizen would go beast mode and just kind of be like "Only those who believe in Hope, cling to hope" and Trunk's "Hope" of winning would just blow the **** up in his face, Aizens words even have powers ._. Not even Goku can do that .-. And that's saying something O..o (By the way he shows this when he says something about Truth in one of the some-what recent mangas so if you want to check on that have a ball...)
Basically all in all Aizen's Reiatsu would make Trunks fall to his knees while Aizen would then forcibly make Trunks suck his dick. That's all there is to it. Trunks doesn't have a chance in hell Aizen's much to god mod, and he apparently can't die. He only got blown up by his own reiatsu when Uruhara did his little plan.. Aizen was unscathed AND only in the crystalis form.
This means that his true power is unknown and is shown to kill humans while he simply walks near them.. Goku can only like blow people away. Oh.. and even if he fuses.. It'd do jack if someone wants to throw Goten in there for some reason? idfk. Just thought I'd mention that.
Oh one more thing.. Aizen is now a God so he can just **** their day up and probably alternate reality now.. I wouldn't put it past him.
._.
LOLOLOLOLOLOLOLOLOLOLOLOLOLOLOLOLOLOLOL AT ALL YOU IDIOT BLEACH FANBOYS, WHEN HAS AIZEN BLOWN UP A PLANET?! King Vegeta blew up three planets by waving his hand, and Frieza destroyed an entire race of planet busting super soldiers and a planet 10X bigger than Earth by pointing at it. Kid Goku dodged light itself, as it was expanding. Kid Goku RAAAAAAAAAAAAAAAPES the entire Bleach-verse, how can they compete with a child that can take bullets to the head and just get a red mark, move faster than light itself, AND PRODUCE THE ENERGY NEEDED TO SHOOT MOON BUSTING ATTACKS MULTIPLE TIMES? Shit, Kid Goku goes great ape and we have to throw in every single character in Bleach just to stand a GHOST of a chance. Goku broke out of Roshi's hypnosis in 8 seconds, which was said to leave people in a coma for YEARS. Aizen has NO chance, against Trunks, who is HUNDREDS OF MILLIONS of times stronger than Kid Goku, who can move faster than light and bust moons/small planets.