Couple of thoughts,
First off; good idea sorting your medical before starting training. Whether an OML will or won't affect your recruitment prospects I can't say.
What I can say is that CAA medical have always been very human and within the rules will do their best for you. They have always been at the forefront of risk based medical assessment, but many other european regulators are not similarly minded and the UK CAA are but one voice in Europe.
That said, regardless of how your medical situation is resolved now, you are joining a career where you ability to work depends on your ability to retain a medical. Rules change, people get unwell, accidents happen. Have a plan B.