I would be so ridiculously happy if that were the case, but I don't believe it is (unless you're aware of any recent developments I may have missed).
Unless there has been a more recent ruling, as of 1st July last year, in order to exceed 12 knots you need the following:
Seats for everyone
Lifejackets for everyone
Thames Local Knowledge Endorsement
Lets not forget my personal favourite.....
If you are on your own its perfectly safe to not have a lookout, however if there are two of you, the lookout must be at least PB2 (with the skipper holding Advanced) otherwise its dangerous!
Also, I should point out the boat would need to be pre-approved by the PLA (i.e. you can't just turn up and assume its okay) as you have to apply for a certificate.
Off the top of my head I can't remember if you have to submit a passage plan too, they were intending to enforce that, not sure if they did bring that in or not.
Of course I would absolutely love to be proved wrong on this, as then I can bring my RIB back to the Thames!