c# online compiling and execution security issues

So I was thinking of writing online c# compiler and execution environment. And of course problem #1 is security. I ended up creating a little-privileged appdomain for user code and starting it in a new process which is tightly monitored for cpu and memory consumption. Standard console application namespaces are available. So my question is this: can you think of ways of breaking something in some way? You can try your ideas on the spot rundotnet.

Edit2 If anyone cares about the code, there is now open source fork of this project: rextester at github

Edit1 As a response to one of the comments here are some code samples.

So basically you create a console application. I'll just post a big chunk of it:

class Sandboxer : MarshalByRefObject
{
    private static object[] parameters = { new string[] { "parameter for the curious" } };

    static void Main(string[] args)
    {
        Console.OutputEncoding = Encoding.UTF8;
        string pathToUntrusted = args[0].Replace("|_|", " ");
        string untrustedAssembly = args[1];
        string entryPointString = args[2];
        string[] parts = entryPointString.Split(new string[] { "|" }, StringSplitOptions.RemoveEmptyEntries);
        string name_space = parts[0];
        string class_name =  parts[1];
        string method_name = parts[2];

        //Setting the AppDomainSetup. It is very important to set the ApplicationBase to a folder 
        //other than the one in which the sandboxer resides.
        AppDomainSetup adSetup = new AppDomainSetup();
        adSetup.ApplicationBase = Path.GetFullPath(pathToUntrusted);

        //Setting the permissions for the AppDomain. We give the permission to execute and to 
        //read/discover the location where the untrusted code is loaded.
        PermissionSet permSet = new P