The changes are backed by promises of more investment and greater freedom for chapters. One of the first significant moves will see the UK Chapter take control of content at next year's European Meetings and Events Conference, in April at Excel London.
"The role of the host community will be more central than previously," said MacMillan. "For the first time the event will be open to non-members and we want to create a truly pan-European conference."
Elsewhere, MPI is launching an online scheme allowing groups to share ideas and create their own 'community'.
MacMillan, speaking at an international press briefing in Brussels, said increased funding would be linked to growth in membership.