so i watched Attack of the Autobots last night and long story short but imagine an aligned-like origin of the 13 primes, and where, like in the aligned continuity, Optimus is the 13th Prime, and the 13th Prime’s information/role/appearance wasn’t anywhere near as well known or defined as the others. But! Instead of just being The Mediator, he’s actually the first cassette host/carrier. He made the first cassettes. I think this also ties in well with the whole “his spark is the most like Primus’s own” thing the aligned continuity thing has going on. He, like their creator, can make smaller bots, but he’s not a god, so they can’t survive fully independently. And it would be very like him to realize that he made a mistake that caused someone else harm, and to do whatever it takes to help them, including giving them access to his own insides to gain what they lack so direly.
all this to say: i think it would be neato if Soundwave & his cassettes found out and were forced to confront the fact that Optimus was the reason any of them exist. And I also think it would be funny if he just didn't tell anyone that he’s universally compatible with all cassettes regardless of whether they have a bond or not, and people had to find out by him just taking one and shoving them in his chest without warning.