also on that - i think optimus and terminus would not like each other. in this au I'm writing where terminus remakes the decepticon political party, he and optimus clash, but terminus is seen as generally peaceful so there's that.
they'd be the best of frenemies. Optimus respects Terminus's closeness to Megatron and Rodimus, but he also is wary of him when he sees that he is actually, convincing Cybetron to allow a Decepticon political party.
And Terminus works with Starscream and it's clear they're together. At this time Starscream and Optimus are friends, but optimus knows that starscream is sneaky and so is terminus, and terminus is worse.
not romantic not platonic but a secret third thing [what would happen between earth and the moon if the earth stopped spinning as illustrated by xkcd randall munroe]
the thing that bothers me about dragon riders is that the dragon absolutely does not have to let you climb on its back. your ability to 'ride' the dragon is entirely dependent on the dragon allowing you to do that. it could fly just fine without you sitting there. which means you are not a dragon rider, not really. that beast is not your pet. you're the dragon's pet. you're its trophy wife.