What you you call a person that can take a simple, easily understood concept or task and turn it in to a complicated procedure?
one that obfuscates
where obfuscate means
to make (something) more difficult to understand
This is often used in the context of intentionally making something more confusing rather than doing so through incompetence, but it wasn't clear from your question which side of that aspect you wanted.
Although it doesn't crack the "proper" dictionaries, confusticate was used by Tolkien in The Hobbit and forms of the word appear in the Urban Free Dictionary. Thus confusticator: one who confuses things beyond their natural state.
Now, before I start getting down votes, how about confuter the noun form of confute: confound [Webster's].
But as long as we're considering neologisms ... confusionist, huh?
a thing that provides resistance, delay, or obstruction to something or someone.
I think this word could be used to label your hypothetical person, but it could also be used to label people who make a bad situation worse.
If Urban Dictionary is an acceptable source, then frustrator would also work:
some who frequently provokes frustration
Hair-splitting is the introduction of unnecessary complications. It is the making of unreasonably fine distinctions. No matter how small, the person will differentiate between subjects.
"The legal experts have a particularly hair-splitting mentality".
Person 1: "Colin just spent the past half-hour telling me the difference between magenta and pink"
Person 2: "He is such a hair splitter"
You've already had general answers like complicator and obfuscator. Here's another slant on your question, yielding a few more specific terms.
As it stands, the question asks for a label for a person who can (i.e. has the ability to) make the simple complex. One label is deep thinker, though such people might prefer to substitute the word profound for complex. For example:
Someone asked: “What is the meaning of life?”
Some random dude replied: “To give life a meaning.” - daedreth, quoted by Nico Lang
If your question emphasises the word procedure, the apparent simplicity may be due to underestimating the problem. Researchers sometimes take simple ideas and produce extremely detailed means of reliably carrying them out. Consider the following thesis which documents how a robot may be set up so that you can simply tell it where to go. It's harder than it sounds - even people don't always get it right. (I got this from a google search and am counting on CMU's reputation for the result's reliability.)
Natural Language Direction Following for Robots in Unstructured Unknown Environments - Ph.D dissertation by Felix Duvallet
For the political cynic, the ability to produce a complicated procedure from a simple, easily understood concept or task is a skill commonly attributed to some bureaucrats.
And finally, we who answer EL&U questions can at times produce quite a lot out of very little :P .