Again, I agree with the principle of what you're saying, but not with every point.
I agree that a new striker isn't our number one priority. Personally I think a genuine left winger is more important than an AM, a position which I think Sigurdsson and Lookman are good enough to rotate in. A left footed player would give us better balance and just a different option, even if it's off the bench. Maybe Dowell could be that player, but if Sigurdsson for example is in the middle behind Tosun then we have the same lack of pace which blighted us this year, and I know Dowell has played a lot on the right cutting in.
I kind of disagree with the idea that all of the players you mentioned have to be immediate first teamers. I don't think Baines is totally finished, so I don't necessarily believe we need to go out and sign Danny Rose or the like for £40m, a good steady alternative who can share left back duties with Baines would be fine in my opinion, same with the attacking position as already mentioned.
I would totally disagree about the coaches. If a coaching team can't decide whether a player is good enough after working with them every day over the summer and watching recordings of previous performances then what are we paying them for? Surely we can't expect them to buy good players who they've never worked with on that basis, because how could they make a judgement? I'm not talking about making a hasty judgement like selling someone after 2 friendlies, just coming in and saying I do/don't think this player is ready to have an impact for us this season. It's a pretty standard expectation of a manager I think.
The 20 goals comment on Tosun was just because that's often used as a yardstick for strikers. 18 would be fine like, but the point still stands. The coaches need to analyse peoples games and decide whether they think they've got what it takes to do what we need. I find the idea of just giving people a chance on the off chance that they prove to be better than you thought a really odd one, but I know a lot disagree with me.