In theory I see only 2 logic scenarios unfolding:

1. Use your .300 on lion and take scopeless .470NE for up&close on buff or ele...
2. Dump .300 and take (scoped

) double for everything in .500/.416 (matches .416 Rigby's balistics), .375 H&H Fl. or Belted, 9.3x74R maybe...

Then there is praxis...

P.S. IMO 450/.400 lacks some speed to be perfect on lion...