Ardent and charging are completely counterintuitive; Ardent grants a speed boost while lowering damage, while charging is slow (removing most of the benefit of +speed enchants) but increases damage. Logically, they should increase charging speed somewhat.
Proposal
Swift grants +15% charging speed
87% charge time
Would also slightly increase energy consumption for charging
Ardent grants +35% charging speed
74% charge time
Same energy consumption, just reaches full charge faster