Same thing with a mule, robo-mule or a self propelled vehicle. Wait, I can detach the bags from a bike/trolley and throw them over the 2m wall with a help of a comrade/short rope. Then goes the 15kg bike or or the trolley. And unless we are talking about the jungle/fallen trees/mountain warfare etc., where probably anything non-human can not be used effectively, you will be faster and less tired reaching the destination. Last but not least: simple trolley is quite cheap, way cheaper than the load it can carry. You can throw it away when the going gets tough.