An alternative speculation to the origin of Life?

The endosymbiosis theory postulates that the mitochondria of eukaryotes evolve from an aerobic bacteria. In recent times, the discovery of the Mimivirus was hailed as a missing link between a virus and a bacteria. However, it is also a fact that the Mimivirus possesses a genome of a size that is comparable to the other bacteria. The mimivirus also possesses genes that are involved in nucleotide and amino acid synthesis, which some bacteria lacked. It also possesses an inner lipid membrane. I was speculating on a model of endosymbiosis whereby the ancestral virion particle like the mimvirus enters a prokaryotic cell. This virus may have accumulated mutations resulting in a defect in assembly of viral coat. As it may have coded for genes that may be beneficial to the prokaryote, it forms a symbiotic relationship with the host. It may be possible that the virus is the ancestor of the nucleus in a modern day eukaryotic cell. Like a nucleus, it can take over the role in controlling the cells.