The word "rudimentary" is the important one here, IMHO. If the goal of a new browser is to match the "market leaders" feature-for-feature, then all bets are off, IMHO.

However, if one changes the starting assumptions, e.g., only seek some basic functionality instead of a carbon copy of the existing browsers (but controlled by some new entity), then the playing field becomes level enough to have meaningful competition.

Another assumption is that all browsers must be "all-purpose". But some could just as well be limited purpose. Arguably we already see an extreme case of this in "mobile apps" which target only one site. Alas, these tend to be non-transparent, not open-source nor easily modifiable and recompilable.

As a text-only browser user, along with non-browser TCP clients, each being vastly simpler than a so-called "modern" browser, I am able to consume a large amount of web content without ever touching Javascript or graphics. That amount has surprisingly increased over time. More and more web content today comes as structured plaintext (JSON) which is very easy to convert into any format one desires.

IMHO, Javascript is likely a black hole for any "rudimentary" browser project. The size of the interpreter and the memory demands, entire classes of security issues that are enabled by Javascript, the list of "gotchas" is long if not endless. If JS is a must-have, I hope it's worth it.