"We have to start at the point that says what is in it for the consumer. That is what we are just unpicking at moment."
He said the rental scheme was "possible" but admitted there were some "technical barriers", one of which is the complexity of some Lego kits, many of which contain thousands of pieces.
"What are the chances of giving them to an eight-year-old child and getting them all back again?" Mr Brooks added.
"There is a lot of technical thinking that needs to be done. We are right at beginning of that."
Mr Brooks said Lego was exploring several ideas with a view to producing the highest value from products while consuming the least amount of resources.
He said many would "probably never see the light of day" and there was no current plan to trial a rental scheme.
Lego has come under increasing pressure to reduce its carbon footprint amid growing international alarm about the impact of plastic waste on the environment.
It manufactures 19 billion pieces per year - 36,000 a minute - that are made solely of plastic whilst much of the internal packaging is also plastic.
So far, the sole breakthrough has been the development of a line of bricks made from plant-based plastic sourced from sugarcane. The green trees, plants and flowers were first included in Lego sets late last year but comprise only one - two percent of the total amount of plastic elements produced.
Henrik Ostergaard Nielson, a production supervisor in Lego's factory in Billund, told the New York Times last year: "We need to learn again how to do this."
Lego reportedly emits around a million tons of carbon dioxide each year, with about three-quarters coming from raw materials that go into factories.
The company has invested more than £100,000,000 and hired 100 people to research non-plastic alternatives.
It is aiming to keep all of its packaging out of landfill by 2025.