@spiffymeister
From an OOC point of view, I would treat it as we did the old Knights of the Merciful Sword. The paladins of Tyr were dominant BY far, and all the top positions were held by said knights. If memory serves, from V3 and to its death, we managed to have a few who became actual knights, but what would in our faction rankings be tier 4, could never be given to Non Tyrrans. And Non Tyrrans had to justify why they were in a dominantly Tyrran faction. In short, non Tyr paladins had a much harder time going places.
From an IC point of view, all paladins of non Lathander would have to bow to the authority of Lathander as the dominant power, but opportunity for paladins of deities who shared some resemblance to Lathanders teachings could be allowed.
Chauntea would make good sense
Milil would too, the shared ideas of creativity
To a lesser extend, I could see the odd Sunite too
Belon could definitely see it as a way of gaining a foothold outside Eveningstar, by "allying" with faiths who had shrines in the city, and it would supplement his waning power, as Paramour stated.