Velleity is a perfect word to describe a wish or inclination which is not quite strong enough to actively pursue or lead a person to action. It can describe an idle wish or passing idea, as well. The plural is ‘velleities.’
Examples of use:
The idea was intriguing, but it remained a velleity.
Their head is full of velleities, but no real plans.
Etymology: Early 17th century. From Medieval Latin ‘velleitas’, from Latin ‘velle’ (to wish).