I found out the solution
first I need to modify
\biserver-ce\pentaho-solutions\system\saiku-adhoc\plugin.xml
And add this
<overlay id="launch" resourcebundle="../content/saiku-adhoc/web/saiku-adhoc.properties">
<button id="saikuAHButton" image="../content/saiku-adhoc/web/images/src/adhoc_32.png"
command="openURL('Saiku Reporting','Saiku Reporting','content/saiku-adhoc/web/index.html?biplugin=true')"
label="saiku ad hoc label button" />
</overlay>
Just before the </overlays>
Then I have to go to
\biserver-ce\tomcat\webapps\pentaho\mantle\launch\launch.jsp
And modify the "onclick new WAQR ..." to:
<td align="center" class="smallButton"><button class="pentaho-button" id="button0" onclick="launch('saikuAHButton', function() {warning('error opening saiku ad-hoc reporting .')})">New saiku Ad-hoc report</button></td>
I can do the same for the image just on the top of the button (because the image is also clickable):
<td align="center" width="226" valign="bottom" class="largeGraphicButton"><img src="images/clr.gif" width="226" height="10"><br><a href="#" onClick="launch('saikuAHButton', function() {warning('error opening saiku ad-hoc reporting .')})"><img src="images/new_report.png" border="0"></a></td>
<td valign="bottom" width="3" class="largeGraphicSpacer"><img src="images/clr.gif" width="3" height="11"></td>
<td align="center" width="226" valign="bottom" class="largeGraphicButton"><img src="images/clr.gif" width="226" height="10"><br><a href="#" onClick="launch('saikuButton',function() {warning('Error opening Saiku Ananlysis.')})"><img src="images/new_analysis.png" border="0"></a></td>
Now when I click on it I have direct access to saiku reporting and analysis, I just have to remove the shortcut for WAQR and analyzer on the menu (which will be easy) and I'm good