it seems that all most of the vintage pens are firehoses by default
They might have been set up so that their ink flow was optimal for vintage iron-gall inks. I believe that vintage i-g inks contained more iron & wrote (even-) ‘drier’ than modern i-g inks do.
My advice to anyone who finds their pen to be ‘too wet’ is, for a first step, to try running a ‘dry’ ink through it.
E.g.s inks such as Pelikan 4001 Königsblau (Royal Blue), their 4001 Blue-Black, or maybe even one of the Edelsteins.
If those won’t tame the pen enough for you, try iron-galls such as R&K Salix or Scabiosa, or the various i-g inks sold by KWZI, or ESSRI, or Diamine Registrar’s Ink.
Only after finding a pen inked with those inks to be ‘too wet’ would I want to send it off for irreversible alterations to its nib and/or feed. Especially on one of the larger (i.e. more expensive) pens like a Pelikan Soverän.
Of course, my idea is of absolutely no use at all if one hates the colours of all the inks I’ve mentioned, or really, really wants to use a ‘favourite’ ink in their pen but finds its flow too-wet for that particular ink.