All sounds reasonable at first but you’re making three specious arguments:
Firstly economies of scale can work in such a way that it’s actually cheaper for BMW to fit heated seats into every car than it is to design, stock and maintain two seat SKU’s. No, I’m not fooling myself, You're just misguided and not aware that costs can work counter-intuitively at scale. You’re right they are for-profit and this is likely why they’re doing this (as well as lowering the price barrier and offering trials).
Secondly, it’s very easy to design subscriptions / software to fail ‘on’ i.e. if the car looses an internet connection it retains its previous state. This is already, as you can imagine fairly common.
Finally, the right of the consumer is the right to choose - which ironically is what BMW are doing here…giving you (more)choices. Nobody is taking that right away from you. The point of every for-profit company is to create value for shareholders. As long as you don’t live in the forest surviving off nature you’ve already accepted this fact. I really don't see what companies making profits and consumer rights have to do with this.
You make a good point about "fail
on" (or shall we say "fail enabled", as it would be disastrous if heated seats failed "on"

). However, an internet-connected seat heating mechanism is fundamentally a more complex device than a "dumb", offline seat heating mechanism. And as someone who works with complex systems for a living, let me assure you: systems that are
more complex are more expensive to build & maintain, and have more possibilities to go wrong.
Also, in no possible universe does the consumer actually
save money under BMW's new scheme. Economies of scale does not mean that eventually it will cost
negative dollars to produce something. It just means that the per-unit cost will approach — but never fall below — zero as the number of units increases. So, if we were to take two different SKUs:
- A regular seat heating mechanism, and
- The same seat heating mechanism, but wrapped inside of an internet-connected padlock
...the latter will always cost more to build.
And if somehow during the development of the latter, they discover a way to actually build it for
less money than the former, then this also means that the
former can now be built for less money too! This is because of the underlying technology involved: there's nothing about seat heating mechanisms that have anything to do with the internet-connected padlock. A seat heater does not
NEED a padlock in order to function, the same way that your wife does not
NEED a chastity belt in order for you to consummate your marriage.
Finally, yes, we as consumers have the right to NOT buy a new BMW, or the right to NOT pay for this ridiculous new feature. That's what I'm trying to advocate for here.