Actually inflation *can* be introduced into bitcoin in a number of ways, at nearly zero cost. The supply cap or 21 million BTC is not "guaranteed by math"; it is decided by humans who choose which software to run. Paraphrasing the old proverb, "no protocol change is prohibited if the right 20 business men decide to implement it".
"Zero cost"... Aside from the cost of nearly every major hodler of bitcoin dumping them instantaneously if the 21 mil cap is put in serious jeopardy. "Killing the golden egg laying goose." "Mutually Assured Destruction." The miners are perhaps the
most incentivized to stick to this rule in the entire ecosystem, after all, they can't dump coins today that they will be mining tomorrow.
The rest of your points seem pretty salient and generate no argument from me.