Several major research groups have been attempting to "build an organism from the ground up". Basically making an bacteria from scratch to perform a single function, such as producing a chemical compound. This area of science is called synthetic biology. They have been able to make some very stripped down organisms, based on pathogenic bacteria that live inside of a host cell. This has all been done with a bacterial model. Bacteria are hundreds, if not thousands, of times larger than viruses. With our present knowledge of DNA replication, you can not fit the required gene encoding DNA or proteins into a virus capsule. It is not physically possible. A virus size organism capable of replication would require a completely different mechanism for replication.