(Note that this is wishlist, and will require some time and transition
work.)

The new 4.18 kernel supports mounting FUSE filesystems as an
unprivileged user, making the suid fusermount binary unnecessary on 4.18
and newer kernels. Thus, once Debian has such a kernel as the minimum
requirement (in a future stable release), the fuse package could drop
support for the suid fusermount helper.

In the meantime, once a 4.18 kernel becomes available, it might make
sense to make the suid permissions optional and disabled by default,
with an option to enable them for compatibility with systems not yet
running a 4.18 or newer kernel.