Take some CD hostages won't have work , all that would done is put admirals and holy knight on there ass.
It won't work?
They value a slave more than a celestial dragons' lives?
Plus this 14 years ago they don't have the man power they have now .
Why do they need man power?
Surely Dragon and Kuma are stronger than Sabo + Karasu + Morley
and they would face less enemies
Sabo with 3 commanders and tons of planning manage to infiltrate MJ thanks to Reverie, which happens once every 4 years(aka 2 years too early for the revs in the past and all escaped injured, sabo nearly dying in the process.
The reverie literally was working AGAINST them because that's when the Marijoa has the most security
Dragon and Kuma surely can get there like Fisher Tiger or even Kuma did by teleporting and climbing the wall, if not just outright learn Geppo and just fly up
And Sabo got hurt because he went for 5 gorosei and Imu, not because he was hurt by regular security