Looking at the broader narrative, the good options are Renxiang and Xia Lin, in that they either follow through on previous developments like Renxiang opening up after dealing with the BINO or the Awkward Tea Party, or they start new character arcs.
There's a huge coincidence (maybe not) between what Renxiang believes her purpose is, and Zhengui's understanding (Without destruction comes stagnation/Without renewal, destruction is stagnation too.) This creates conflict with Xia Ren, who's only used destructive language when talking about reform ("To preserve the past is stagnation. Stagnation is death." and "The rot of ages breaks easily with a well aimed blow[...]"). This opens up Xia Lin for an interesting character arc in that she seems to be interested in understanding her people's traditions before Xia Ren came along, and how that trucks with Xia Ren's perspective.
Gan is an okay option, in that it would be really opening him up for a lot more narrative focus since his dream would, for narrative purposes, have to be him not failing in the tournament and getting to join Renxiang in the Inner Sect. Meng Dan is a complete unknown and narratively lacks enough connection to Ling Qi to even really justify putting it up as an option.
[X]Cai Renxiang
[X]Xia Lin