How to break the save system?

To disable the save and load buttons, you can edit the files -
[UI\SaveLoad\SaveSpecific\Save.(WindowMSButton).xdb] remove the command

				<Commands>
					<Item href="/UI/SaveLoad/Save.(UISDirectRunReaction).xdb#xpointer(/UISDirectRunReaction)"/>
				</Commands>

and 

				<Commands/>

similarly, remove the command for loading in [UI\SaveLoad\SaveSpecific\Load.(WindowMSButton).xdb].
And for double-clicking [UI/SaveLoad/LoadsList.(WindowScrollableContainer).xdb]

		<Commands>
			<Item href="LoadDblClick.(UISDirectRunReaction).xdb#xpointer(/UISDirectRunReaction)"/>
		</Commands>

As for [quickload 'F8'] and [quicksave 'F5'], nothing can be done about them—these commands are hardcoded into the exe. Of course, you could break them there too by using a HEX editor to change the values, for example to quicklo1d and quicksa1e. But that's not a great option.