I like Flygon ideas quite a bit, actually.
Ignoring the obvious synergy the deltas have in common with each other, you've got non-delta option of Vibrava to spread damage, you've got non-delta Flaffy for energy attachments, and you've got the Flygon delta EX for cleaning up after a Ampharos Jamming spread.
The problem? You've got two stage 2 lines to hunt out. But they can be searched for by Fearow. And you've now got pokemon like Corsola, Stantler, and Smeargle whom make EXCELLENT starters for a deck like this.
On the other hand, what synergy do the other listed partners have with Ampharos? Electrode only takes a prize if you're doing him against most stage 1s (but not Blissey or Magmortar), meaning that he's dead weight against big Stage 2s. Though you gain a rainbow energy through use of him, you're losing 2 energy just to deal the 100 damage attack. :/ You also will have to discard the rainbow with use of Ampharos's attack, which makes Electrode not that useful.
Venomoth is an interesting card. Venomoth IS resistant to fighting, which is a big thorn in your side. Of course, so is the Flygon line. Of course, Flygon EX d is super effective against most fighting types AND most psychic types. Of course, Venomoth is not spreading damage, nor is it particularly good at finishing off multiple pokemon, so it's not really assisting Ampharos.
Finally, Delcatty. Out of the three you've listed, this might be the most useful, as it packs draw power and a way to return those lightning energies that Ampharos will wind up discarding. Delcatty's usefulness really comes from swarming the SW. Of course, as Jamming's non-stackable, I don't see much point in swarming with Ampharos SW. I do see a point in swarming with Flygons and two Amphys (one of each type), but not with SW.
Questions?