What do you call a person who suggests ideas?

Solution 1:

One of my pet hates, but no-one said that neologisms are unacceptable even if I'd scrub out my mouth with wire wool rather than use this one in real speech:

Ideator

A person who creates productive ideas, a conceptualist

One who ideates; one who holds or generates an idea, or synthesizes a concept

https://www.urbandictionary.com/define.php?term=Ideator

https://en.wiktionary.org/wiki/ideator

"Ideation". I ask you. Mutter, mutter, grumble.

Solution 2:

Idea Woman

idea man

a person with an unusual capacity for visualizing and formulating new techniques, approaches, products (MW)

Solution 3:

I'd call such a person an innovator.

A person who introduces new methods, ideas, or products.
‘he was one of the great innovators in jazz’

Reference:
https://en.oxforddictionaries.com/definition/innovator