Hello there, and welcome back to the game (although I'm hardly a veteran myself)!
Whilst I would echo the point that within the current state of the game these two cards are perhaps best incorporated competitively in two independent strategies (e.g. Yveltal / Zoroark / Gallade or Lucario / 'Bats), I would also heavily support TuxedoBlack's sentiment of "Just try it anyway!" because that's the fun of the game. Not sure if this is the place for it, but if you were to build a deck with those two cards as the centre, I would suggest the following cards for your decklist:
Pokémon: Lucario EX and Yveltal EX of course, Yveltal (XY) / Carbink BREAK (FAC) / Landorus (FFI) for energy acceleration, Gallade (BKT) for draw support and as a non-basic attacker, and Shaymin EX (ROS) for draw support. Oddly one of the first cards that came to mind was Volcarona (AOR), although I'm sure people would object to that. Whilst M Lucario EX does suffer from the Spirit Link / not-amazing-attack problem, why not if you want to?
Items: If you're likely to run Double Colourless and Strong Energy maybe Puzzle of Time would be helpful, Battle Compressor is a must for the attack-based energy acceleration, maximum counts of VS Seeker and Ultra Ball are a given, and Fighting Fury Belt is probably a strong choice as well, although Focus Sash wouldn't be the worst.
Supporters: With Lucario EX you could utilise the amazing Korrina, as well as including the usual combination of Professor Sycamore and N for draw support, with perhaps one-of counts of Lysandre, Hex Maniac and others which you could access via the VS Seeker / Battle Compressor combo in a pinch. Including Gallade would also warrant the inclusion of Maxie's Hidden Trick Ball if you want to go that route.
Apologies if this comes across as super condescending, just trying to lay out my thoughts on what cards I'd consider essential if you opted to build this deck! I take a fair amount of offence to criticism of fun decks due to their (lack of) competitive viability, but then I don't really play competitively so what do I know? My point is basically just "YAY FOR CREATIVITY!" and I'd be interested to see what you come up with, hope I was more help than zero!