There are legal considerations and there are linguistic considerations as to whether a brand name can be used as a generic common noun.
Whether it is possible to 'brand' what is not a brand name and insist it only be used with initial capital letters is a legal, not a linguistic usage question. That would better be answered elsewhere.
There are good reasons for not using brand names generically if you are in the UK civil service, as I once was. In published papers or report, we are strictly forbidden to write 'power point' or even 'Power Point' in a public document, even though it became a 'household' expression. This was for the good reason that government officials and the government itself must not promote or remotely even seem to be promoting a commercial product. That is a very good reason, but again, not relevant to the rules for capitalisation.
The convention is for brand names to be capitalised. So we buy a Ford Fiesta rather than a ford or a ford fiesta. But there are obvious exceptions, of which the hoover is one, which has even become a verb. Another is fibreglass which was once a brand name of the company that invented it; another is the filofax. We buy cheddar cheese in lower case, even when we have bought it from the Cheddar Valley.
This is a very interesting limiting case for language usage. Fifty years ago, most of what came into the public domain was managed by some sort of editorial process, which enabled some sort of rules to apply a measure of consistency in a matter like this. Publishers of journals, government papers even major company publications, as well, of course, as books, were subject to some form of checks, often subject to style guides of some form or other. The balance of control over the past 25 years or so has been rapidly swinging away to the individual writer, sometimes edited, often not.
We have to ask whether there is any reason for trying to 'restandardise' usage (if it was ever standardised in the first place). By reason I mean pressure of circumstances or consequences to render it likely that people act consistently in this regard. It is difficult to see what that would be.
If there is a common principle, it is probably that where someone thinks of something as a 'generic' or 'household' thing, they will write it with a lower case initial letter; if they think of it as a branded product, they will use an initial capital.
You write uzi, I write Uzi; you write mercedes, I write Mercedes: let's call the whole thing off.