Since Yoshi has admitted the code is a mess and its a combined mass from several different third party developers and a partial rewrite in house, yes its spagetti code. Also, the decisions for how worlds communicate has to be made very early in the development process. If you don't specifically set it up to allow for it then yes you do need to rewrite significant portions of the code to make it happen later; it is not as simple as adjusting a firewall or IP setting. Its taken the devs a long time to give things like cross world friends lists and LS because they have to sort out the spagetti code and rewrite it to allow for those things. While not impossible, it would be hugely impractical to have cross datacenter parties and thats before you even consider things like latency.