Anyone had the equipment customized ?

Yes; kinda, maybe, sort of.   Being a electrical design engineer, I design a log of amplifiers and analog control electronics at work.  So naturally, I do this at home with some of my equipment.  For a while, I was doing custom electronic design for folks who had high end stereos. 

The key is finding where the weak spots are in the equipment, then making those spots more robust.   By weak spots, I mean where the designer left performance on the table and didn't pack it into the product.   Anyone can tweak stuff, which may or may not sound better, and may not give you much bang for your buck.   And, trust me, hiring someone to do custom engineering on your equipment is expensive. 

If you go this route, pick someone who routinely modifies your brand and model often.   That is, they have a long history of fixing that particular model.   Ideally, they should be someone who actually worked at the factory or someone who worked in their service dept.  If they don't meet this criteria, don't send them your equipment or money!

I have had Steve McCormack mod and upgrade his equipment, which I would consider 'customising', as I can pick and choose what I want done.

B

My tube amp and linestage were from a builder that only does built-to-order units.  For the linestage, I could specify whether it would actually include a phono-stage, whether the output would be capacitor coupled or transformer coupled (or both options available), the type/brand of input and output transformers, etc.  I chose a preamp (includes phono-stage), transformer inputs and outputs, I asked for remote control of volume (something the builder had not offered before), and I requested a balance control (implemented by utilizing two big Davin controls).  The custom amplifier has matching/complementary transformer inputs.  I initially got the amp with Langevin input transformers, but later, I went with Western Electric input transformers (the amp is essentially a rebuilt Western Electric 133a amplifier).

My speaker has been modified by me.  The midrange horn and compression driver have been replaced by a vintage Western Electric horn and compression driver.  This was easy to do because the horn in my system sits on top of the woofer cabinet on a totally open platform  The replacement horn actually looks better than the original because its 24" width exactly matches the width of the woofer cabinet (the original horn is smaller and weird looking).  I added an L-pad attenuator to control the output of the horn driver.  I will be doing additional modifications, including a totally new (but made out of vintage parts) crossover and top notch wiring for the speaker (probably Audio Note Sogon wire).