I think what he meant isn't dynamic moves like Necrozma's or G-Bro, but actually standard "uses Defense instead of attack" calcs like Body Press
I think Ironmage understood that! Their response - to me - seemed to be that doing this would remove the drawback that usually comes with investing non-attacking stats. Instead of there being a "tradeoff" - "do I invest in Defense to take hits better or in Attack to hit harder?" - you can now invest in one stat to do both at once. They were proposing an Electro Ball-esque move that incorporates two stats at once as an
alternative solution, and one that they would like more, not as the way they interpreted Imperial Magala's post.
Currently, EVs and natures are set up so that a Pokémon has to
make choices in the "build triangle" of power, bulk and speed - there's no way to max out all three. But compressing power and bulk into one stat or power and speed into one stat means you aren't ever giving up one for the sake of the other.
They weren't opposed to the idea happening a few more times, of course - this was just their reservation with it being
common.
Personally, I think it would still be quite interesting! I'm already a big fan of mixed attackers that have key moves on both sides and can't afford to focus on just one - I think it'd be neat if you had a Pokémon that could invest in just Speed for its main STAB but still needed Attack for its coverage, for example (
especially if it also had a physical STAB that would outclass its Speed-based one, but only if it had significant investment in Attack as well). It actually creates more incentive for tradeoffs if you're meaningfully rewarded for each one - most people wouldn't consider foregoing offensive investment in a Pokémon that's meant as a sweeper or a cleaner, but if the rewards of Attack investment were subtle enough that it wasn't a death sentence to forego them...
Well, I feel like more people would be open to the trade of "a bit of power from your coverage moves for some bulk, but your best move is still okay" than the trade of "the power of all of your relevant moves (which you need) for some bulk (which still won't be very impressive)," you know?
This is also something that's neat about Pokémon with more extreme base stats - the higher the base stat, the less EV investment in that stat matters and the more freedom you have to choose to invest in other areas. Stats other than Speed are codependent enough that you can have weirdly lopsided stats without actually changing the power level - like how a Pokémon with 181 Attack and a 90 BP STAB isn't that different from a Pokémon with 140 Attack and a 110 BP STAB, or you can have the same bulk as Shuckle with 20/230/230 or with about 100/120/120 depending on investment. I may be wrong, but I think that's why Pokémon like Mega Garchomp and Black Kyurem could get away with being mixed attackers - investment mattered little enough on their higher offense that they could afford to sacrifice it for their lower one - which is something I always think is fascinating when I look at stats!
I also think it's interesting that the hypothetical move for Blissey and Gallade was proposed for their
Special Defense, which is their higher defensive stat by a great margin - most Pokémon prefer to invest in their lower stat (Blissey especially! it usually runs max Defense as far as I know, and I don't think it ever really invests in Special Attack anyway, so it's not like there's any loss there), so this proposal actually creates a new tradeoff ("do I invest in the defense that needs it more [bulk at the cost of less power], or do I go all in on the defense that also boosts my moves [full power at the cost of gaining a critical weakness]?").
Meanwhile, Gallade as it is would... basically never consider investing in Special Defense in the first place? Its Attack is higher
and it has one of the best physical STABs it could want - it strikes me as
very unlikely that the option of
giving all of that up to invest in Special Defense would ever be strong enough to outclass Attack investment in the first place. Even so, it has the potential (with a good enough BP) to introduce a niche for a new alternative spread that
still is losing power in exchange for bulk - just in a way that's less comically inefficient and more worth considering, given that the new move is good enough. That actually introduces more tradeoffs rather than eliminating any!
So yeah, uh... this is getting a bit off-topic from the thread, oops, but short answer: I totally get what Imperial Magala is saying, and I'm with you on it! but I also think you may have misunderstood Iron Mage's point - I think they also fully understood what Imperial Magala was saying and were addressing legitimate potential cons and alternative solutions, not just misinterpreting it. C: