Re: Penny wise, pound foolish
That tallies with what I've heard, though I'd go a bit further and note that as far as I'm aware, the code missing from the original ROM was mostly orientated around peripherals, and I've not heard of any contemporary plans to build a new ROM with better BASIC performance - though there were no shortage of third party alternatives and "compilers" to boost the speed of your programs.
Equally, modern "homebrew" patches have mostly revolved around fixing known bugs and adding new functionality. I dont recall anything related to BASIC performance - at this point, if youre still interested in writing stuff for ye olde Speccy, you're likely to be using assembly or some higher level toolkit.
Otoh, I'm always happy to be pleasantly surprised!