I think the problem with assigning another priest or paladin as the PC's adviser was basically spelled out in the original post. The previous head of Solku's Sarenites retired and left the PC paladin temporarily in charge (suggesting she was likely the highest ranking paladin available).
Any adviser-priest or paladin is probably going to have to come from outside of Solku, and since it is the most prominent stronghold of Sarenrae in Katapesh, probably outside the region, which is also more complicated by Sarenrae not having that strict of a church hierarchy (IIRC). ie, the priests in Solku don't really have anyone further up the chain of command, though there are definitely more powerful clergy elsewhere.
Moreover, we have the situation with the PC inquisitor, which complicates matters. Right in the class description, inquisitors are permitted a bit of leeway when going outside of their religion's ethos, but the PC took an already shady plan and turned it into attempted murder.
So, there are a few things that need to dealt with. Solku is a stronghold of Sarenrae, and was founded by Sarenites. It is perfectly legitimate in my mind for their clergy to be tried by the church. In fact, it would not surprise me if that were a tradition of the city. It also doesn't surprise me that exile/excommunication would be a punishment for these kinds of crimes. Sarenrae is a diety of mercy and healing after all.
That said, given that the crime was again another religious leader, I think the lord of the city was more than justified demanding this be handled by him. I think the punishment dealt out to the paladin was extremely harsh, particularly given that he was doing this to the interim head of Sarenrae's faithful in Solku, among which I believe Lord Kel Kalar counts himself. I could see this harming him politically.
So, the net result here seems to be that the inquisitor was excommunicated and exiled by the church, but the paladin was exiled by the city council.
This seems to me that it would provide a good opportunity for both PCs. Since the paladin will be protecting this remote town for a few years, she likely won't have access to someone who can simply cast commune. However, if she still has her powers, she can be reasonably sure that she acted in good faith.
I'd still suggest a hound archon arrive in this remote town to act as an adviser. Sarenrae obviously doesn't intervene in mortal affairs directly very often, but a faithful servant from the celestial realms is a clear sign of approval at a time when the paladin is probably at her lowest.
Moreover, this might be a good time for the inquisitor to grow as well. Class directives or not, the inquisitor clearly acted against Sarenrae's teachings, and I wouldn't be surprised if the goddess had stripped some or all of his powers. Yet, if the paladin intends to act against the church establishment in Solku, she might be able to use the inquisitor's help, and thus help him redeem himself. Paladins do have to walk a stricter line than inquisitors, and someone more worldly or politically inclined could be a great help in the days to come. Unless he's just a crazy murder hobo, because his previous actions could indicate that as well ;)
(BTW, thanks for starting this topic. I generally avoid the boards this days, but have run a campaign in and around Solku previously, so I find it an interesting area, and like contributing to the discussion.)