The short answer to part of your question is yes...there are commercial medical kits of all sizes and sophistication. A quick Google search should give you plenty of ideas. And as has already been said, the complexity of your medical kit may in fact depend on your level of expertise and training. Perhaps more important then the kit is the training (which may dictate the kit). If going to a remote area consider taking a Wilderness First Aid (16 hours) or Wilderness First Responder (40 hrs) course. These are specifically aimed at activities where calling 911 is not an option and even more then skills teach a way to look at a medical/trauma incident in a remote area. There are also marine-focused medical courses (for example: https://www.wildmed.com/course-type/...ency-medicine/
). Once you get the training, then deciding on what you are comfortable with in a medical kit becomes easier. Another thought, most vessels need more than one medical kit. Consider that having a basic first aid kit for the minor cuts and scrapes is useful so one doesn't need to dig into the main (and larger) kit; similarly a first aid kit on your tender or dinghy is a good idea.
Finally you ask about a defibrillator (AED). While an AED can play a major role in someone surviving some types of cardiac arrests, consider that if you are in a remote area you may lack access to the advanced medical care required to continue that recovery. There is a decent discussion of AEDs on boats at: https://www.aedleader.com/best-aed-for-boat/
(no endorsement intended!).