How to change a policy that's has always been this way but needs to be changed now?

I’m a member in a local community which is associated with multiple associations above it (think of it like statewide, nationwide and so on). There are a lot of layers to the community. However, the local community is mostly self-governed and independent, only few policies are internationally standardized across all communities.

One policy that has been standardized since the founding year is when you are allowed to join a local community. After a few decades, this was changed to loosen it up a little bit. This change was based on a high consensus among all levels so the change didn’t create quite a backslash. Furthermore, the change was still standardized so every community had to adhere to it and couldn’t make any individual changes.

Now this policy has been changed again. However, instead of an addition of a policy, a current policy was simply removed. This change hasn’t been highly controversial (as in paralyzing the whole organization or it would be the only topic right now) but it does indeed incite some emotional discussions. The removal of this one policy affects the whole process of someone joining our community as it was one of the definitive formal rules to decide when somebody is allowed to join.

We now are advised to design our own joining process without this policy in place, meaning the international standardization is mostly gone. In our country, we have decided to at least have some common ground, a guideline is being developed right now. However, it isn’t mandatory to follow the guideline once it’s out.

In our local community, this change also had impact. Some feel the removal of the policy was right, some don’t feel that way and yet another group of members want to take the opportunity and design a new process altogether. The only thing certain right now is that we have to change the policy (by which it’s also allowed to return to the old rule as long as it has a majority). Generally, more seasoned members favour to return to the old policy while newly joined ones favour the removal.

How can we get everyone onboard with a possible policy change? How do we avoid to upset long-time members when the old policy isn’t reintroduced? How do we avoid a vice-versa situation where the old policy returns on our local level and younger members are upset that everything is "as it has always been"? How can we take into accounts the members concerned with designing a new process?