They were only improved in one aspect, with regards to drug resistance but still essentially the same in most other respects to the wild type. It would take more mutations responding to more kinds of stresses for a broadly stronger variant to emerge.

To simulate that would be even more irresponsible because then we are moving into the realm of new bacterial species and the Pandoras box of potentially weaponized bacteria that the human genome has never seen before.

HIV aids virus when it first emerged was like that. Ebola mutations do similar things.

Animal and plant immune systems are in a constant evolutionary arm race against bacteria, viruses and the like.