[capink]

Use the Action Chains plugin. It has and open with action based on this plugin, but it supports template language which can do what you want.

Make a chain withe single action (Open with action), and configure the action by choosing the path to desired program. After that choose the template option and enter the following template:

program:
	priority = 'CBZ,CBR,EPUB,MOBI,AZW3';
	paths = formats_paths();
	for fmt in priority:
		path = select(paths, fmt);
		if path 
		then
			path;
			break
		fi
	rof

You can assign this chain to whatever keyboard shortcut you wish. It should open format based on your priority variable.

Notes:

• Change the order of the formats in the variable highlighted in blue to the order as you wish.
• The formats should be in UPPER LETTERS.
• If you don't want the chain to be available for books without these formats, you can set a condition on the chain as follows:
  

  template = copy the same template above
  datatype = text
  comparison = "!="
  condition value = Leave this empty

  Also, check the "disable menu chain if condition is false" check box.