I would replace these 10 Johto filler episodes to focus on Ethan as the secondary rival: Ep122 (Bellossom), EP135 (Sunflora), Ep148 (Wooper), EP164 (Pidgey), EP172 (Ledian) EP197 (Smeargle), EP218 (Diglett), EP234 (Xatu), EP260 (Slowking) and EP267 (Vincent) Episodes focused on Silver/Team Rocket could've been 2-parters which would replace these ones: EP132-133 (Marill and Sentret). These 2 are between Ash defeating Falkner and leaving Charizard. EP177-178 (Yanma/Skiploom), EP202-203 (Natu/Smoochum) and EP243-244 (Igglybuff/Slowpoke). Give Marina a 3-parter focused special right after Ecrutreak: EP184-186 (Murkrow, Remoraid, Teddiursa). Replace other episodes for Casey and Gary and make these 5 rivals + main trio all present at Whirl Cup. The goal here is to treat Ethan as Barry whose cameos are more spaced out but still welcoming to watch.