Only need one defender in RD2, RD3 & RD4, so find five to seven def rookies and then worry about it closer to RD5.
Most enjoyable part of the season is playing around with all different structures until it all goes downhill when the real thing starts.
So from here and other sites the popular ones appear to be :-
Travaglia * , Allan * , Busslinger , El-Hawli , Leake , Reid , Jepson
so who knows there might be enough
add in the more expensive Schoenmaker , Milera , Sinn etc price types
Or what about the other way
Rankine , Macrae then 6 rookies
Just using Lynch , SPP , Curtin , Martin , Kako * , Berry as price points
Hewett * , Davidson , Erasmus * , Hall * all popular and cheaper.
Start one of Daniel , Parker & Smith as Flex and the other 2 in the mids
Chase the rookies depending which line looks more plentiful