'has been much thought' is correct and can be used in written English.
You could use this phrase when you want to indicate that a particular subject or topic has been extensively considered, discussed, or contemplated. For example, "The environmental implications of this new policy have been much thought."
There has been much thought devoted to how experimental animals have been bred, but up until now, little attention to how they have been fed.
Folic acid deficiency is associated with high homocysteine levels, which has been linked to an array of neuropsychiatric disorders, including depression and dementia and there has been much thought paid to the use of folic acid in improving cognitive function in the elderly, especially in the case of dementia (Reynolds 2002).
There wouldn't have been much thought then given to courting women voters, let alone African American women voters, who were crucial to Barack Obama's wins in 2008 and 2012 and are necessary for Clinton to win in 2016.
Stephen Sondheim's grimly funny blood bath of a show, which opened on Broadway in 1979 and has been much in our thoughts ever since, is opera for those who expect it to be.
During the silent era there does not appear to have been much serious thought given to the question of why there might or might not be women working as motion picture camera operators.
Whoever started it off, two millennia ago, can't have been much of a thought leader.
The program, seen on Saturday night at the New York State Theater, should have been much more fun and thought-provoking.
"In my own work at universities I have been much struck by the paralysis of thought induced in pupils by the aimless accumulation of precise knowledge, inert and un-utilized.
Though it's unlikely these thoughts would have been much clearer than your average Minister.
From the start, my work has really been about exploration, so there hasn't been much thought into the conceptual basis of my projects.
Not for 2,000 years of rabbinic Judaism had there been much thought of female rabbis, but the first ordination took place soon after the movement shed its fresh light on the meaning of equal souls.
