We have a software base we can expand from NOW.
And 68K software can run pretty seamlessly on a PPC.
If you doubt me, check out a MorphOS or AOS4 demo.
Next to endianess you also have the packing of data types in a C struct. The native packing of PPC and m68k is different so the seamless running of m68k on PPC is only possible because special non-PPC native packing is done on data structs that are to be used by legacy m68k software on PPC.
On AROS we preferred efficiency over backwards compatibility and at the time PPC AROS was live we decided to always use native struct packing. This means m68k software does only run under emulation on AROS PPC.
Although different AROS devs have different opinions I still stand by this choice. People who want a PPC Amiga-like OS with seamless running of m68k software can already use MorphOS or AOS4.
I do think emulation of m68k in AROS can be more integrated using a system like on Linux now: if you want to run 32-bit programs on a 64-bit system you need the 32-bit libraries used by that program. For the rest the program will show up as any other program. So to run m68k on a AROS with another CPU you need the AROS m68k libs but the GUI will be shown next to native programs, DOS mounts are shared, clipboard is shared etc.