I hate building equipment...I'd rather spend my time brewing.
It's not for everybody, I agree. I like riding motorcycles I hate working on them. But if you build your system you can build it to meet your specifications rather than have to brew to another's visioned specifications. And when you hack into it and change it you will not feel reluctant to make those cuts or weld.
For instance I have a 1.5 bbl system that we built back when we first started YHB. We have cut and added to the frame a few times (added a tippy dump, shortened it, added casters, etc).
As far as personal customization goes, I wanted an electric HLT but gas BK. I started with a 55 gallon MT with a custom made false bottom then switched to a Blichman MT and false bottom. Well, the 55 gallon fabbed false bottom works WAY, WAY better than the Blickman MT false bottom so I switched back to the original.
We swapped out burners 2 or 3 times till we found the burner that works best for our system and welded ports, thermowells etc where they worked best for us. Adjusted pump location several times, added a PID.... you get the picture.