This script removes some Share header items in a share-header.get.js customization. Currently there does not appear to be a utility to remove widgets from the new JS widget model, so this is what got the job done for me...

share-header.get.js

var widget, widgetsToRemove = [ "HEADER_SHARED_FILES", "HEADER_MY_FILES", "HEADER_PEOPLE", "HEADER_TASKS", "HEADER_REPOSITORY",
        "HEADER_SEARCH" ], idx, max;

for (idx = 0, max = widgetsToRemove.length; idx < max; idx++)
{
    findAndRemoveIn(model.jsonModel.widgets, null, null, widgetsToRemove[idx]);
}

function findAndRemoveIn(obj, arrContext, arrIdx, id)
{
    var idx, max, key, removed = false;
    if (obj !== undefined && obj !== null)
    {
        if (Object.prototype.toString().apply(obj) === "[object Object]")
        {
            if (obj.hasOwnProperty("id") && obj.id === id)
            {
                if (arrContext !== null && arrIdx !== null)
                {
                    arrContext.splice(arrIdx, 1);
                    removed = true;
                }
                else
                {
                    logger.debug("Unexpected match outside of array structure: " + jsonUtils.toJSONString(obj));
                }
            }
            else
            {
                for (key in obj)
                {
                    if (obj.hasOwnProperty(key))
                    {
                        removed = findAndRemoveIn(obj[key], null, null, id);
                        if(removed)
                        {
                                break;
                        }
                    }
                }
            }
        }
        else if (Object.prototype.toString().apply(obj) === "[object Array]")
        {
            for (idx = 0, max = obj.length; idx < max; idx++)
            {
                removed = findAndRemoveIn(obj[idx], obj, idx, id);
                if(removed)
                {
                        break;
                }
            }
        }
    }
    return removed;
}