xpath : test if node is the only child other than specified ok elements

I want to write an xsl template that checks to see if a given node is the only child node, other than certain specified elements :

in this example, <target/> will be changed to <hit/> as it is the only <target/> node, and only <ok/> nodes precede it

<root>
<!-- this is ok, the ok nodes are at the top, followed by only 1 target -->
<mynode>
    <ok1/>
    <ok2/>
    <target/>
</mynode>

<!-- will fail, bad element before target -->
<mynode>
    <ok1/>
    <ok2/>
    <bad/>
    <target/>
</mynode>

<!-- no match, multiple target nodes -->
<mynode>
    <ok1/>
    <ok2/>
    <target/>
    <target/>
</mynode>
</root>

I was using this xpath :

<xsl:template match="target[not(following-sibling::*)]
                       [not(preceding-sibling::target)]
                       [not(preceding-sibling::*[starts-with(name(), 'bad' or 'hello')])]
                 ">
    <hit>
        <xsl:apply-templates/>
    </hit>
</xsl:template>

In that last predicate, do I have to indicate specifically any node I don't want? Can I something like

not(preceding-sibling::*[not(starts-with(name(), 'ok'))])

thanks