Again I'm behind this all the way except for one Counterspell being, in effect, beginning-to-end faster than another.
Why is that weird to you? If you have a sequence of magical runes, and deactivating the runes requires you to erase half of them, then a longer sequence would take longer to erase half of it. Why
shouldn't the parameters of a Counterspell take into account the spell being countered? Whenever I've read about spellcasters countering spells in fiction, they're always pulling apart the energy patterns that their opponent is weaving, which requires a different process for every spell being cast.
The
only time I've seen a single, universal Counterspell - that doesn't (necessarily) depend on the spell being countered - is
in MtG. And D&D is
supposed to make more sense, with closer reflection of genre conventions, than a card game. You shouldn't automatically
expect that Counterspell is literally the same discrete entity which happens to work on every single spell being cast.
As for the rest of the issues, they're solved by the example I explained. If you're countering the spell
after the chanting and gesturing, while it's in flight to its target, then the caster
is physically capable of casting another spell because the part that
would render them exclusive (the verbal and somatic components) are over. So it doesn't
necessarily defy internal game-world logic, unless you choose an in-game reality where it
would; you only see the conflict because you
choose to see an in-game reality where the spell is being countered
while the chanting and gesturing are still happening.
It's a lot like the problem I had with 4E, and again with 5E, regarding heal times. If I
choose to describe damage as bloody gashes, then it doesn't make sense for that to go away in a couple of hours. The problem isn't with the system - both systems are fairly consistent(ish) in their in-game causal logic - it's just that their logic doesn't match up with what I
want it to be. In order for everything to make sense, either I need to get on board with how they are doing things, or I need to update the rules to reflect what I want them to be.
You have the same choice: either get on board and change your perspective of what's happening in the game world, or change the rules to reflect the model you're actually using.