Farhan, apart from the usual length, diameter and so on measurements of each component, (with photos if possible), the absolutely crucial measurement is any threading requirements between the nib/feed/housing (referred to collectively as the section) and the pen barrel. This often scuppers any plan to make up a custom pen because each manufacturer uses their own proprietary threading and a custom-made tap/die may be required, at a cost measured in hundreds of pounds. That's before we even START making the pen!
Also, threads cannot usually be cut in wood because wood is too soft and the threads tear out. So if you must have mahogany pens, you'll be paying someone to make a wooden 'sleeve' over a resin pen structure - an expensive undertaking requiring years of experience.
I'm not telling you what to do, but here are my thoughts:
The 'kit' pen Alex quoted to make for you comes with a reasonably good steel nib plated in 22kt gold. For a £50 pen it's more than good enough. Even more so as it will have 'Iridium Point Germany' stamped on it (often abbreviated to IPG in this industry) leading the recipient of the pen to believe that it is German-made. (It's not - it's Chinese, but that's our little secret!) Iridium, by the way, is the metal used to make the tiny 'blob' at the end of the nib which comes in contact with the paper. ALL nibs use Iridium or some metal in that family because they are super hard-wearing and prolong the life of the nib. Especially so do gold nibs have Iridium points as gold is a very soft metal and would wear out in minutes or hours.
If you absolutely MUST have a solid gold nib (with an Iridium point, natch) then I highly recommend that you go to
The Golden Nib and buy the SMALL nibs from him. Just buy the nibs, nothing else. Then Alex can swap the kit nibs on the pens he has made for you for these solid gold ones. The reason you should buy those nibs and no tohers is that we know for sure they will fit on the kits you wanted from Alex. Shaeffer or Waterman nibs are designed to fit Shaeffer or Waterman pens, and are unlikely to fit the Baron kit.
Any other approach is going to cost you far more. This is the same advice you got from IAP (and no doubt from the other forums you've tried too). I hope this answers your questions.
David