In light of the recent rumors (which do genuienly seem like more than rumors) that Keaton may be returning to the cape and cowl, not just in the upcoming Flashpoint movie, but also potentially for multiple appearances in future DC films.
How would you like them to approach Michael Keaton's return as Batman?
Thomas Wayne/Flashpoint Batman: Considering the movie he's appearing in, this may seem the obvious choice. There's a long proud tradition in DC media of superhero actors returning to play the hero's father in a reboot (Adam West as Thomas Wayne in the Brave and the Bold cartoon, John Wesley Shipp as Henry Allen on The Flash) and this would be the biggest example of that. It allows Keaton's Batman to continue to be a distinct character and potentially co-exist alongside Pattison's Batman in future films.
Bruce Wayne/Batman from the Burton films: Basically, a continuation of the version Keaton played in the Burton films, potentially ignoring the Schumacher films with other actors. I guess in a way this would be the most fan-pleasing option (akin to Brandon Routh's recent return as an older version of his Superman). And there are certainly ways to make it happen, with the Multiverse and alternate timelines. But keeping this Batman around beyond the Flashpoint film raises challenges. There's already the conflict between the Affleck and Pattison versions to address - throwing Keaton's version in only adds to the continuity nightmare. Though I dare say there can be ways around it.
A new version of Bruce Wayne/Batman: Not an explicit continuation of the Burton films, but a new version altogether. Maybe the Batman Beyond Bruce (a fan favorite option). Or a DKR Bruce. Maybe just a future time-traveling version of Pattison's Bruce Wayne. Again, this raises questions of how to keep the character around, though it'll be a lot easier to present this Bruce as a possible future/alternate version of Pattison's Batman, than to inject a version from a different franchise altogether into the DCEU.