Can I start a business while on 457 visa and staying with current employer?

Hi, my name is Niall, I'm 31 years old, from Ireland and have been living in Australia for over 5 years so far.

Originally I worked a mechanical design engineer and in the last year I moved to a technical sales role for a new company. My sponsorship got transferred and they applied got me a new 2yr 457 visa, approved a few weeks ago.

While waiting I tried to go down the PR route but my skills assessment through Vet Assess got rejected last month as my experience is not sufficient and my degree in technology with design is not relevant which has put a halt on my PR hopes. My next option is getting 2 years with my existing employer and gaining PR through them. That is 15 months away.

I want to start a protective motorcycle clothing business with a friend who is an Australian citizen and ideally we would like to register it together as partners. I have seen similar topics from a few years ago but think rules may have changed since then and I'm hoping for an answer specific to my situation.

If I stay with my current employer who sponsor me and work full time with them can I be a partner in my own business outside of this? If not I'm keen to hear any other options. I don't want to wait 15 months plus for PR, realistically by the time I would get it, it would be 2 years.

Thank you in advance for any answers or advise given.
Niall