can also add that i have been playing around a bit with doing it from code

[TinyMCEPluginNonVisual(
PlugInName = "DefaultSettings",
AlwaysEnabled = true,
ServerSideOnly = true,
EditorInitConfigurationOptions = @"{

and the global editor.css (that you point out from Admin)

table {
EditMenuTitle: Styles;
EditMenuName: Skanska table;
border:0; margin: 0 0 0 0;
border-spacing: 0;
border-collapse: collapse;
line-height:14px;

}

Maybe EPiServer have to change some things in the table.htm in order for us developers to be able to add custom classes from code?
http://stackoverflow.com/questions/11203896/own-default-table-style-in-tinymce

If I understand your question correctly then you're pretty much there. To add classes to the table classes dropdown, add your classes to the editor.css, remembering to prefix them with 'table' for example:

table.grey-table {
    EditMenuTitle: Tables;
    EditMenuName: Grey Table;
    background: #ccc;
    border: 1px solid #999;
}

table.blue-table {
    EditMenuName: Blue Table;
    background: #ccf;
    border: 1px solid #00f;
}

Thanks Paul.

All i missed was to give it a name i.e. table.name