I think Jack Steele would be a general benchmark for Kennedy's trade value. JS nominated StK before trade week, after finishing his initial 2-year draftee contact. Hmmmm, sounds familiar. So, how do they stack up?
Steele
Bid at pick #16, cost #24 to match
Played 17 games over first two seasons
At GWS avg 14.9 touches, 4.8 tackles, 2.3 clearances
Trade cost: Future 2nd (assumed at ~26-30, ended up #26)
Kennedy
Bid at pick #13, cost 34 & 40 to match

Played 19 games over first two seasons
At GWS avg 16.0 touches, 4.1 tackles, 2.2 clearances
Trade cost: Future 2nd? (assume ~21-25, will end up #36

)
Differences
Stats almost identical, including senior games
Kennedy spent less time playing NEAFL in year 2 (more highly regarded?)
Carlton's 2nd rounder likely to be lower than the Saints pick was expected to be, so maybe we could argue a 2nd is too high a price to pay
We could accept a dump of celery
Ahmet Bains is no SOS
Conclusion
At best will cost a 3rd, but could cost a 2nd (with minor steak knives coming back?). All bets are off if Griffen/Scully/others are included.