When you invest so many pts on a
BL for your
WL youd wanna keep them out of combat really. SO I would recomend droping
BL on one and getting 2
BL+
EML WLs and one pure Swordlord to tag team with the Avatar. Might wanna get a Cannon for gaks and giggles tho

. But as I said before, I think two units of
WGs are superior to path finders. They cost 45% more but 100% more resilient against
str 4 fire. Not only that, for instance a single deep striking land speeder will whack your whole pathfinder unit in one go. I also think Eldars divination ability is really useful in a wraithwall army since it really lacks mobility.
Regadring the 2vs2, there are no official rules from what I know. But the most common practice is to allow all negative effects between the two teams but none of the positive. So fortuned Assult termies will usually not be possible.