Everything that we've seen so far indicates a fairly high level of point investment to run them at all, compounded by the fact that if you indeed want to throw a ton of points of Seers with the expressed purpose of rolling a 5 on a chart, Most people would probably be ok with that.
I guess if the plan is to take 400+ points and just have it sit and hide for that final turn objective grab on stuff without OS in a glass cannon army that needs to make the most of it's hitting power then ok.
There wont be a "jetseer" unit. The only one who can have it is the troupe master. If you want to JOIN some Eldar IC's TO that unit...well, the ONE you'll get from your allied detachment. Ok. Enjoy not having half your special rules anymore for that unit. The only stuff it can affect are things that can join the Troupe itself. Which is few and far between.
Crazy, they didnt let the Harlie ICs roll more than a d3 on that table. Almost like balance or something.
EDIT: Though on that note, joining certain PLs to one of those could be not terrible. What with having a 2+ armor buffer and a few of them being CC beasts. Now with 100% more Veil of Tears and Stealth/Shrouded!