Adding Missing Elements

Hello,

I wanted to get some opinions on the best way of doing something in xsl.

I have an element <node> which has a certain set of attributes and child
nodes that will always be there.  However, it has an additional <list>
child element, that may or may not be present with varying child
elements so <node> could have variations like this...

<wrapper>
	<node id1="5" id2="bar">
		<name>myname</name>
		<value>myvalue</value>
	</node>
</wrapper>

<wrapper>
	<node id1="5" id2="bar">
		<list/>
		<name>myname</name>
		<value>myvalue</value>
	</node>
</wrapper>

<wrapper>
	<node id1="5" id2="bar">
		<list>
			<item>A</item>
		</list>
		<name>myname</name>
		<value>myvalue</value>
	</node>
</wrapper>

<wrapper>
	<node id1="5" id2="bar">
		<list>
			<item>A</item>
			<item>B</item>
		</list>
		<name>myname</name>
		<value>myvalue</value>
	</node>
</wrapper>

Given these possible variations and based on some processing elsewhere
in the document, I would like to make sure that <node> always has
<item>B</item> in its list...possibly adding <list> if it is not
present.

Can someone give me some suggestions on the best way to do this?

Thanks,

Matt