Cook up, so to speak

• Think of
• Take part in a think tank
• Make plans, maybe
• Conceive a notion
• Form a picture of
• Picture in one's mind
• Just think of something
• Come up with something
• Think up

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Ideate \I*de"ate\, v. t. To form in idea; to fancy. [R.] The ideated man . . . as he stood in the intellect of God. --Sir T. Browne. To apprehend in thought so as to fix and hold in the mind; to memorize. [R.]