Make the fire pot's wall/s completly vertical to avoid ash build up.
Make shure there is no horizontal part at the fire pot's bottom to pile the ash. I mean no moving horizontal part.
Make shure all the ash falling down go in the ash pan. Some deflectors can be easily placed under the outside of the grate so the ash falls at the right place.
Make a sort of sliding out ash pan and sliding lid like Vermont Castings stoves have.
Top and front loading doors.
Long gases path like in the base burner with damper to direct the flue in direct or long path mode.
Build in MPD.
And make a beautiful stove...so you can admire the stove 12 months of the year
Most of the items mentioned here can be found in many antique stoves.
Good luck