why not ionic plugin update ? so my own solution here.

update-plugin.js

#!/usr/bin/env node


var fs = require('fs');
var child_process = require('child_process');

if( process.argv.length != 3 ){
    console.log("usage: " + process.argv[1] + " packagename");
    process.exit(1);
}


fs.readFile("plugins/fetch.json", {encoding: 'utf8'}, function(error, data){

    if( error ){

        console.log("readFile plugins/fetch.json error, are you in an ionic project directory ?");
        process.exit(2);
    }
    else{
        var pkgname = process.argv[2];

        var pkgcfgs = JSON.parse(data);

        var config = pkgcfgs[pkgname];

        if( ! config ){
            console.log("no such plugins installed: " + pkgname);
            process.exit(3);
        }

        var url = config.source.url || config.source.path || config.source.id;

        var variables = config.variables;

        // console.log(url);
        // console.log(variables);

        if (!url){
            console.log("don't know how to fetch the plugin, please report a bug");
            process.exit(4);
        }

        var cmd = 'ionic';

        var rm_args = ['plugin','rm', pkgname];
        var add_args = ['plugin', 'add', url ];

        for( var k in variables ){
            add_args.push('--variable');
            add_args.push(k + "=" + variables[k]);
        }

        console.log("removing current plugin ... ");
        var rm_process = child_process.spawn(cmd, rm_args, {stdio: 'inherit'});

        rm_process.on('close', function(){
            console.log("adding new version plugin from " + url);
            var add_process = child_process.spawn(cmd, add_args, {stdio: 'inherit'});
            add_process.on('close', function(r){
                process.exit(r);
            });
        });
    }
    
});