bigscoot,
Diesel engines are different from gasoline engines in many ways. First of all it's not a question of compression ratio, that can kill your gasser bottom. It's the way different burning characteristics of injected diesel fuel. It's like a tetonation, that's why all diesels engines have to deal with that. Old engines with indirect compression had small compustion chamber combined into the head of the cylinder to prevent destroying the piston. That chamber had only a small part of it opened to the engine's combustion chamber and piston itself. Modern engines has combustion chamber build in the piston itself and injection of the fuel is divided in few stages. First stage is to heat up the combustion chamber and move piston slightly down, then the second one (and every other following the first one), gives the power and torque. That's why diesel engines have such high torque, because combustion last much longer than in gasoline engines.
You can see the difference on these pictures:
Indirect injection diesel
Notice the glow plug in the precombustion chamber.
Direct injection diesel
Like the guys said before you'll need some solution to heat up the combustion chamber to start the engine. It's possible to start diesel engine with just cranking it but it'll be much easier with the air heated up before.
Another thing you've mentioned is the camshaft. First of all you need to make sure that your valves won't meet the piston, which will be much closer to the cylinder head than in gasser.
Another idea that you could consider is to build a two stroke diesel engine. That was done many times before, maybe not in such small scale, but maybe that will be easier to achieve? Two stroke diesel with big and heavy flywheel. Should work IMHO. It won't be so fuel efficient though. But you'll have work cycle per every rev of the engine.
You can find some info here:
DIESEL LOCOMOTIVES
Anyway interesting project!
Last thought of mine. You can find some more info of two stroke diesel cycle engines looking for small engines for RC models. Maybe you even could use one for your project? These engines are very small, light the only disadvantage is they rev like crazy
Good luck!