Gas masks and full body suits are nothing new in One Piece and given Luffys resistance to poison after Impel Down he probably have an advantage over anyone else if they have to fight in a poisonous environment (well besides venomous type themselves but than, Cesar wouldn't be of much help...
Crocodile was after the Ponoglyph in Alabasta because they can tell you how to obtain a super weapon. Kudos reasoning to find Raftel might be, to obtain such a weapon to help him with his suicidal tendencies.
I think you forgot it was clearly established there is no way to navigate how you want without a Log Pose, even with Namis navigational skills. You would also only have a 33.3% that the second Ponoglyph is on the opposite side of the X otherwise you would ride along the sides to your goal.
That...
