If you're defending against "random wealthy person wants to subvert the network" then I think you're right. You make it cheaper for them at the same time it's cheaper for you. Your defense is adding more people (or at least more money for legitimate mining), not technology.
On the other hand, if you're defending against e.g. the NSA, then they already have the ability to make their own hardware like this, so you're not helping them any further.
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It would depend on your supposed adversary.
If you're defending against "random wealthy person wants to subvert the network" then I think you're right. You make it cheaper for them at the same time it's cheaper for you. Your defense is adding more people (or at least more money for legitimate mining), not technology.
On the other hand, if you're defending against e.g. the NSA, then they already have the ability to make their own hardware like this, so you're not helping them any further.