yeah i've seen people use an approach like eric mentioned but more just for when you dont want to pay the increase to a full license and instead just pay for employee center licenses. that at least gives you some better control over security concerns. but yeah, none of this is supported/officially recommended and if NS found you were doing major customization to get around paying them they might stop you, so proceed at your own risk. and as sandii says, likely the effort involved to fully build it out isn't worth the tradeoff, unless maybe like 50 of your users only interact with one record type or something. but most users need access to various parts of the system to create/edit records, run searches and reports, etc so you end up rebuilding a ton of functionality within a suitelet or something.