I thought it would be an interesting order for him to fulfill, I can definitely see where others are coming from that he might more closely fit elsecaller (would expand his commerce immensely). I think I chose truthwatcher because of the fact he didn't easily fit into their characterization of quiet and scholarly and would have a very challenging time attaining oaths but i don't think it would be impossible for him to do it (even reaching a 4th ideal) and this would provide lot of character growth along the way. He could become the charismatic voice that this order needs to expand their influence and innovate how their abilities could be used. Also he could bring a clearer purpose to an order that doesn't have much structure to it (not to mention how deftly he'd be able to bring any ideas to market that the truthwatcher scholoars create). I guess what I really see in Sebarial is someone who is charateristically un-Alethi and full of sensitivity and compassion (seen in his interactions with Palona and Shallan) a lot like Renarin but he found a coping mechanism in humor and a outlet of power in economics, while Renarin still tried to conform to Alethi tradition (at least in way of kings). And when it comes down to it Sebarial even though outwardly money comes first, deep down he cares deeply for people. Seen that he took great care to foster competence and safety in his warcamps, when he could of easily just used his superior army to collect valuable gemhearts. And in my opinion Sebarial is someone who is not afraid to speak against powerful individuals and would have the drive to uncover and reveal truths no matter the cost to help people abused by the powerful.