At least Cynthia requires DIFFERENT Super effective moves. Lance's entire team crumbles to Rock, and most of it to Electric or Ice (dude's more of a Flying Specialist than Falkner is).
I disagree. Not because you’re wrong, but there aren’t that many Pokemon available with good ice and rock moves in their learnset, and tms were more limited in HGSS
Additionally, you had to have enough coverage that it could withstand 6 strong Pokemon. Lapras could only take out 2-3.
In Platinum, you had access to most good tms pre-postgame without having to spend hours grinding Voltorb Flip
I admit part of it is probably down to Cynthia being more of a stat check with her higher level curve, but honestly every mon on her team is a pretty solid one for Gen 4's era of release (bearing in mind that Garchomp was the first non-Legendary Uber in Smogon history off its power, not simply collateral from Evasion Clause). It's basically what they were trying to achieve with RBY Blue except not constrained by half-finished level-up movesets.
In general, I think varied-type Champions are a better final challenge than type-specialists like Lance, Steven, or Wallace, and I'm glad they didn't continue trying to make that a thing after B2W2 Iris. The Elite Four are type specialists with differing focuses so your team requires variety to get past them (barring extreme overleveling), making a Mixed Champion more effective as a final exam than just "the biggest one-trick" in their League.
That would make sense, but pre-fairy, Iris and Stephen presented the most challenge to me as Champions, because with Stephen I hadn’t had to fight many steel types during my run and lacked sufficient coverage, and again in B2/W2 I struggled because I hadn’t thought about the Champion, and didn’t have ice coverage on my team beyond Samurott, who was unable to sweep due to the power level.
Dragon makes for a good champion type because you were facing psuedos with the only SE coverage being Ice and Dragon, both of which were hard to come by.
Cynthia and Ghetsis/N weren’t as hard. When you only have 1-2 of a type, you naturally will have ways to hit their whole team for SE damage. However, when you only have 1-2 Pokemon who can do that, you have to find out of the box solutions for the other Pokemon you’re facing, especially when they have counters to your Pokemon with SE coverage