I have thought about making something like this also. Maybe start with a dolly with an extended base that can locked down while being used as not to have it tip over when loaded. Now, add a dual rail vertically to hold a set of forks like a fork lift. The forks may be lifted with a crank cable hoist, inexpensive 120 v hoist you can get at HF, or similar. Use it as double line and it should do the job. The base and forks should either fold or be removable for easy transport of the dolly. Plus the dolly can be used to transport the oven even up steps.