Oh no, he definitely actively framed Trucker. He opened a Swiss bank account in his name and then transferred money into it to make it look like the mob? military dictatorship? that was running San Felipe had paid him off to sign off on the faulty airplane parts. Interestingly, this is one of the few (maybe the only) times when Clay did something like this in order to cover for someone other than himself. He had no idea what was going on in San Felipe until after the crash; it was Cabot who knew about it, but he couldn't afford to do anything to rectify the situation because AE had lost so much money earlier in the year because Amourelle put out a toxic face cream.
I think they would have gotten past any guilt via the knowledge that Trisha would have given the relationship her blessing because she loved them both and because if she had to chose someone to stand in her place as Christopher's mother, she would have chosen Stacey. Dinah Lee taking on that role, on the other hand, would have had her spinning in her grave if she was actually in it.
Personally, I would have gladly taken a Trucker/Stacey relationship if it had gotten her away from Buck. I liked Buck/Stacey well enough in their first go round, but once they broke up he went off and had all these other storylines while she was reduced to just... waiting around for him, month after month for the better part of a year, until he finally got himself together and they reconciled. And even then they broke up and got back together several more times before she died.
Funny that Trucker and Buck each ended up with the exact woman that Trisha and Stacey, respectively, would have been most annoyed to see him with.
I usually detest older man/younger woman pairings, but I loved Clay and Steffi together. I think it helps that the relationship makes a lot of psychological sense, given that Steffi's father had basically cut ties with her, leaving her desperate for a father figure, and Clay was still struggling to come to grips with having forever lost his opportunity to be a real father to Trisha.