Can {Vorel of the Hull Clade}'s ability potentially double the number of loyalty counters on a planeswalker?
No because vorel specifies artifact, creature or land. The PWs that can turn into creatures {gideon jura} and {gideon champion of justice} or whatnot can be targeted when theyre a crsature however. The rest of the PWs cannot benefit from vorel.
Unless you want to go through the trouble of {march of the machines}+{mycosynth lattice} or some shenanigans to make them creatures