Organisation for enforcement of GPL3 licensing

I wish to find or start a project which is capable and willing of enforcing the GPL3 licensing terms of of individual software developers and documenters (hereafter "contributors") who otherwise have no incorporated or organized identity.

The contributors could be
making contributions small in scope;
large in number;
legally unable or merely unwilling to assign copyright to a central organisation;
unpredictable and unreliable in time and degree of participation and contactability.
Some may come, contribute, and vanish.

I presume that the contributors would be willing to assign rights or privileges to a central organisation, including rights to:
enforce licensing terms,
receive the proceeds of successful litigation and be the sole beneficiary thereof.

Is Software in the Public Interest suitable for that?
Is there another organisation suitable for that?