If you care a lot about substitutes and you don't want to sacrifice them ... that's another story.

As for my team , I always depend on 11 players + 3 substitutes and the rest of my players are just for training bonus ...

If the exchange that I was suggesting above works for free or even for 10-20 tokens it would be a great deal.
Once you get the scout you put him on starters so you will always have 14 spots and the opportunity to sell 14 players.
and you continue the process as much as you have tokens...

Again if it works , it would be much cheaper than buying a scout directly for 39-49-59-69-79 tokens - don't you think so ?