We'll have a great captain, experienced legend but his batteries will be depleted near December to keep us higher places in the table, not to mention keeping us to compete for Europa or FA Cup. Ten Hag will demand a lot fo work from everyone and not everyone will be happy, even though it's a group of supposed professionals.
Putting all faith on Ronnie is a bit similar to putting all responsibilities on Cavani or Ighalo. We'll need an impact sub in mood of Solskjaer / Chicharito at least to keep him fresh.
Alternative could be signing goalscoring RW... think both striker and winger are needed since Martial is passionless vessel for football.