Playing with Abouyamang and Lacazette (or Giroud) up front in itself wouldn't be a terrible idea really.
I think Arsenals best formation they could currently play (without Sanchez) would be a diamond midfield like this, diamond:
Lacazette - Giroud
Ozil
Wilsher - Ramsey
Maitland - Niles (probably)
Kolasinac - Fuckup1 - Fuckup2 - Bellerin