[whpalmer4]

One workaround would be to use an Applescript to open your OmniPlan file and attachments. If you copy and paste the code below into the Applescript Editor (found in the Utilities folder of your Applications folder), edit the path in the first open statement to point to your file, and save it as an application, you can just launch the application you made, and it will open that document in OmniPlan and open all of the attachments in the document.

tell application id "com.omnigroup.omniplan"
	
	open "Users:YourNameHere:Desktop:Sample OmniPlan document.omniplan"
	
	repeat with thisOne in every attachment of front document
		open thisOne
	end repeat
	
	repeat with thisOne in every task of front document
		try
			tell thisOne
				open every attachment
			end tell
		end try
	end repeat
	
	repeat with thisOne in every resource of front document
		try
			tell thisOne
				open every attachment
			end tell
		end try
	end repeat
	
end tell