Disagree.
Let's say Grabban breaks his leg today. Back in training in March at the earliest.
Who would say with confidence that this won't wreck our promotion chances? Being left with a 35 and 18 year old, both with poor recent scoring records?
To score enough for promotion we are looking for around;
20 goals from the two main rotating forwards
10 each from the three attacking midfielders
Another 10ish from the defensive midfielders
5-10 from the defenders
Another 5-10 from squad players.
That gives you 70-80 goals.
The most reliable scorers need to be the forwards and ideally they should beat that 20 goal target to make up for others not hitting there's.
Here's the point- can you see Murphy and Brereton scoring 20 goals between them? I cant- they certainly didnt last year.
Can I see Murphy and Oliviera doing so? Yes, definately. Oliviera will be good for 12-15
We have Soudani also. My point is Olive is not an out and out goalscorer. Although I agree with your sentiment about having someone good to replace Grabban if the worst happens I don't think Olive is the right recruitment