Hi Jago,

It seems that we need to customize all the links and buttons of salesforce standard relatedlist component. as said earlier is to take a help of a custom controller and update the vf page accordingly ( takes more dev time ). overriding by the help of javascript is not recomended as this is not reliable. ( takes less dev time ). If really works for you i would say great!!!

1.2.4. :- you have to work arround with javascripts. Do you know I did it for you :)
 

<apex:page StandardController="Opportunity" showHeader="false" tabStyle="opportunity">
 <apex:includeScript value="{!$Resource.jQueryMin1dot3}"/>
 <style>
     /* to hide submit for approval button */
     input.btn[name="piSubmit"] {
            display: none;
     }   
      /* to hide recall button */
     input.btn[name="piRemove"] {
            display: none;
     }          
 </style>
 <apex:form>
     <input value="Recall Approval Request" id="recall" class="btn" type="button" title="Recall Approval Request"/>
 </apex:form>
 <apex:relatedList list="ProcessSteps"/>
 
 <script>
     var jeet = $.noConflict();
     jeet(document).ready(function(){
         jeet('a').each( function(){             
             if(jeet(this).text().trim().indexOf('Show') != 0){     
                 var addr =  ''+jeet(this).attr("href");             
                 var idx = addr.indexOf('retURL');
                 if(idx != -1)
                  addr = addr.substring(0,idx)+'retURL='+'{!Opportunity.Id}';
                 jeet(this).attr("href", "#");
                 jeet(this).bind( "click", function() {
                      window.parent.location= addr;
                 });
             } 
         });
         jeet('.tertiaryPalette').css("background-color", "#ddb929");
         jeet('.secondaryPalette').css('border-top', '3px solid #ddb929');         
     });
     function correctRetURL(s){
         var idx = s.indexOf('retURL');
         if(idx != -1)
          return s.substring(0,idx)+'retURL='+'{!Opportunity.Id}';
     }
 </script>
</apex:page>

• Remove all the standard button from the related list using css tricks which i have shared before.
• Add your custom button on the visualforce page and  on the action method by the help of [SELECT Id, ProcessInstanceId, ProcessInstance.TargetObjectId FROM ProcessInstanceWorkitem WHERE ProcessInstance.TargetObjectId =: oppID]; you can get to know recall button will be available or not. if it returns a record then show the button so prepare an url "/04i90000009lwcT(Process id by soql )/e?et=REMOVE&retURL=0069000000fBh20 (current opportunity id)"  
• OR if you want to do it by JS add these method inside the ready call

• jeet('.pbButton input').each(function(){
               if( jeet(this).attr('name') == 'piRemove' ){
                   var addr = ''+jeet(this).attr('onclick');     
                   var testUrl = addr.match(/'(https?:[^\s]+)'/);
                       addr = testUrl && testUrl[1];          
                   var idx = addr.indexOf('retURL'); 
                   if(idx != -1)
                    addr = addr.substring(0,idx)+'retURL='+'{!Opportunity.Id}';                 
                   addr = addr.replace('navigateToUrl','window.parent.location=' );                  
                   jeet('#recall').bind( "click", function() {
                        window.parent.location= addr;
                   });             
               }
           });

  
  Seems almost I did you project... Enjoy..