I’ve never been paid any other way than monthly. But I think if I were paid more than once a month I’d try setting the summary period to fixed cycles (e.g. 1st to 1st rather than payday to payday) and set custom budget rather than budget based on income. Would this not work for you?
If you do need fortnightly summary periods, there’s already an ideas thread for this
I’m not sure what you mean by add additional regular incoming payments. If I have more than one income payment in a payment cycle they all get classed as income. Perhaps you could explain the issue further and what you think the solution should be.