Managing resources in lookup filter

Question

My client wants to be able to filter jobplans with the selected asset. To be able to do that, I have developped a function that filters the results based on the custom resource jpassetsplink:

filterJobPlansForLookup: function(eventContext){
   var workOrderSet = CommonHandler._getAdditionalResource(eventContext,"workOrder");
   var jobPlanSet = CommonHandler._getAdditionalResource(eventContext,"jobPlanResource");
   jobPlanSet._lookupFilter = null;
   var assetSet = null;
   var assetnum = null;
   var itemnum = null;
   var jpAssetSpLinkSet = null;

   //CommonHandler._clearFilterForResource(this,jobPlanSet); 
   
   var siteid = workOrderSet.getCurrentRecord().get("siteid");
   if(siteid == null){
    siteid = UserManager.getInfo("defsite");
   }

   if(workOrderSet.getCurrentRecord() != null){
    assetnum = workOrderSet.getCurrentRecord().get("asset");
    assetSet = CommonHandler._getAdditionalResource(eventContext,"additionalasset");
    CommonHandler._clearFilterForResource(eventContext, assetSet);
    assetSet = assetSet.clearFilterAndSort().filter('siteid == $1', siteid)
    if (assetnum != null){
     var asset = assetSet.find('assetnum == $1', assetnum);
     if (asset && asset.length>0){
      itemnum = asset[0].get('itemnum');
     }
    }
   }
   
   var filter = [{siteid: siteid, status: "ACTIF"}];
   if (assetnum != null){
    jpAssetSpLinkSet = CommonHandler._getAdditionalResource(eventContext,"jpassetsplinkResource");
    jpAssetSpLinkSet._lookupFilter = null;
    CommonHandler._clearFilterForResource(eventContext, jpAssetSpLinkSet);
    
    var filteredJpAssets = null;
    if (itemnum == null){
     filteredJpAssets = jpAssetSpLinkSet.clearFilterAndSort().filter('assetnum == $1', assetnum); 
    } else {
     filteredJpAssets = jpAssetSpLinkSet.clearFilterAndSort().filter('itemnum == $1', itemnum);
    }
    
    Logger.trace("[WODetailExtensionHandler] Found " + filteredJpAssets.data.length + " links out of " + jpAssetSpLinkSet.count() );
    if(filteredJpAssets && filteredJpAssets.data.length>0){
     filter = [];
     filteredJpAssets.data.forEach(function(jpAsset){
      filter.push({jpnum: jpAsset.get("jpnum"), siteid: siteid, status: "ACTIF"});
     });
    }
   }
   jobPlanSet.lookupFilter = filter;
  }

With the right circumstances this code works. There are multiple problems with it though:

1- When searching for an asset, the resulting filter is applied to the resource and cannot seem to be removed. If I search an asset in the asset lookup, when the execution gets to this function, the resource data is still filtered and calls to CommonHandler._clearFilterForResource, assetSet.clearFilterAndSort() or directly changing the _lookupFilter property does not work. This sometimes results in the impossibility to find the selected asset in the asset resource, thus the filtering ends up failing.

2- Not searching and directly inputing the desired asset leads to another problem. Since there is no filter on the resource, only the number of entries specified by pageSize is loaded. In my case, pageSize is set at 2000 for the asset resource. That means if the selected asset is not in the 2000 first entries, it is not found by the function, thus the filtering fails.

3- If the filter manages to work, it seems to block further filtering by jpnum or description in the jobplan lookup.

To conclude, here's my question: Is there a way to manage resources so that these problems do not occur ? Any tip is appreciated.

Thanks,