Also higher performance on low-end hardware (currently x86-only, but potentially other platforms if it is completely rewritten in C).
IMO, mobile devices could benefit from a port of both UAE and a rewritten Fellow. The latter could make smoother Amiga emulation possible on more phones and other pocket-sized gizmos which might not sport GHz-level performance yet. (While UAE would give more compatibility.)
A "PSPFellow" could massively outperform PSPUAE for many Amiga 500 games. Goodbye slowdown.
P.S.
On an old Windows 98 PC or laptop, a combination of WinUAE 1.4.6 (or earlier) and WinFellow (latest release/snapshot) is perhaps the optimum setup for Amiga emulation. Together they are a powerful force on old hardware!