If you are looking for subtle changes (such as lighting an bolt-on accessories) then it may help up-lift your bike for less than the cost of changing your machine.
Anything more than the above than it is pretty safe to say... no.
We customise/build bikes because we want ours to be different than anything else out there. Anything bespoke and "one-off" will always be more costly than just another bike rolling off the production line, but this is why we do what we do and the most exciting part about it.
Points to consider here that when the main bike manufacturers mass produce bikes and accessories (I know from personal experience), they have lots of time to design, develop and test an engineered solution before they hit the "go-button" and mass produce items in a more cost-effective manor. When we build one-of-one bikes we have to carry out this process for one bike at a time and sometimes the neatest and simplest solutions have taken the longest time to get to.
You commission a custom bike build because you want something unique and tailored to your personal preference and style, there is definitely not right or wrong answer and you only have to justify it to yourself (and possibly your better half!!).