Joe Joyce's piece is almost the same as the Warlord in my game For the
Crown (the Warlord is allowed to return to its own square, though I don't
think I've ever seen someone exercise that option). I priced it slightly
lower than the Queen, but that's only because I believe long-range moves
are more important in For the Crown than in FIDE; I will still often
promote to Warlord over Queen (since the promoted piece is already on the
enemy back rank).
I've found it's important to plan your defense against a charging Warlord
at least a turn or two before it arrives. (Though in For the Crown, that
usually means "drop some pawns in front of your King", which doesn't
translate to FIDE.)