Are the hacking/boarding mechanics unique to the Legionnaire or will they be available to other electronic warfare platforms?

The combination of hacking/boarding is part of the Legionnaire's default setup/behavior. So while other ships may be able to get the hacking ability, it would be at the cost of other blade-controlled electronic warfare roles, whereas the Legionnaire has it built in. For example, you could "upgrade" the Vanguard Sentinel to support ATC hacking but you'd need to manually EVA over to board after that.