If they are so insistent against a racebox, then do this for SP AND MP
Where the speed lap grid is, when you select one of the boxes, it asks you to select
1) speed lap
2) single race
3) time trial
4) zone (speed class wouldn't matter, just track)
5) combat
You could do this easily for single and multiplayer. Options would be nice on each of these selections after, but at this point, standard racing on these on each mode would be good.
Obviously, RACEBOX is far superior to this, but at least this would allow you to race what you want in both single and multi player.
Options for these modes for laps, weapons, assists would make in a replayable game for wipeout enthusiasts ( us). Things like create tournaments off the box grid would also be welcome.