The requested mon. Its greatest trait on dragon is the ability to help sit on ground, and while it isn't perfect enough to solo it w/o Latios' help (especially in checking Lando-I), it does make the matchup far less of a 50-50 hell against Excadrill. Beyond the ground matchup, Hydrapple and Bolt together make water near unplayable for the opponent. Some less obvious roles of Hydrapple is its ability to come in on pokemon vs normal/steel/dark and force helpful damage/kills. After 2 nasty plots vs Normal, giga drain starts outhealing Blissey seismic toss, and no other pokemon wants to take the fickle beams. Fickle + EP forces steel to sack mons or atleast force them to take heavy enough damage for Gouging and Bolt to win lategame. Against dark it has the ability to come in against the tinglu/sableye defensive core and fire off dangerous attacks. Spread lets it live Archaludon Draco Meteor, +2 defensive Gholdengo Make-It-Rain, LO Landorus Sludge Wave, and Great Tusk Ice Spinner.
Main defensive core, with Archaludon handling threats like Chien-Pao, Gouging Fire, and Kingambit, while threatening/breaking Normal, Dark, and Dragon. Gouging's spread allows it to take 2 specs Greninja ice beams, 2 specs Zoroark-H shadow balls, and 2 LO Valiant Moonblasts. With the teams collective power against Steel, and lots of steels having Balloon Heatran, I felt dropping Flare-Quake coverage was ideal here, and instead having Gouging use its stabs to be more threatening into Flying, Dark, Normal (watch for ditto), and the mirror. Speed hits 409 after a DD, right above out-of-rain Barraskewda, most Zamas, Chien, and Flutter.
Wisp Dragapult is great and all but only truly feels mandated on fighting weak teams; between Hydrapple, Bolt, Breaking Swipe Gouging, and Latios, I felt the fighting matchup was fine enough to turn Dragapult into a speed control option for the mirror + otherwise weak ghost matchup. Coverage over twave is fine, but I found scarf twave is good to get yourself out of bad spots against Valiants/Flutters that are too healthy to OHKO with Dragapult (and assuming Bolt is dead). Also, twaving Articuno in the flying matchup lets Raging Bolt handle it way better, being faster than its subs/hazes/roosts.
Mr Matchup Flip. Great into fairy, being able to CM up multiple times if you get it in on Klefki. Great into flying, helps force out/kill Scarf Enamorus and then break through the type. +1 Draco has a roll to plain OHKO Gliscor, or alternatively you can just switch to Hydrapple, and use it to dent the incoming Corviknight (with lucky Fickle Beams) for Latios' Luster Purge to be free. Many directions to take that matchup. Helps against more offensive waters/rains that Hydrapple struggles to solo, and can be devastating lategame vs Fighting as well.
Feels very necessary right now, even with Hydrapple you want a strong ground immunity for the likes of Landorus, and Latios more immediately muscles through types like Ground/Fighting/Flying. Thunderbolt tends to be pretty free into flying, with most players not wanting to risk Gliscor dying when you have a Raging Bolt.