For ex : England vs South Africa vs Ireland and Windies playing 1 series. Simultaneously New Zealand vs India vs Afghanistan and Bangladesh playing with each other. Similarly Sri Lanka vs Pakistan vs Australia and Zimbabwe or Netherlands. This would help small cricketing nation with the finance and experience as well.
On CSA vs CA tour cancel drama
CSA seeks ICC's intervention over Cricket Australia's withdrawal
With travel restrictions in place, the boards may take a negative stance towards such series. An additional team means more logistics and expenses. And I am not sure whether such series will be included in the ICC ODI super league or not. According to the schedule by ICC, each team needs to play the other a total of 3 ODIs. And I am not sure whether the matches in tri/quad series will be included in this requirement.
Even the current ICC head made an announcement last year that he prefers bilateral series to tournaments involving large number of teams. The preference from the big 3 teams is also towards bilateral series. They are also concerned that the addition of any team (outside the big 3) may reduce the financial value of the series and make it less attractive to the TV broadcasters.