I agree with your main point there
CJJ
, but I think at the point of 25 registered (meaning all above 21 of course) and fully able-to-contribute players you run the risk of cordoning off vital opportunities for youth. It seems to me that many of our problems last year dealing with injuries that you correctly point out, were only compounded by some of the selections we let go out on loan last season as well as the fact that Sherwood preferred a two-man central midfield. I know Holtby wanted more playing time, but we shouldn't have allowed it given what we knew about Dembele and Sandro's respective fitnesses, as well as the fact that at the time Paulinho was still knackered because of Cuntlie Adam. It was just stupid, and Sherwood lamented it himself at the end of the season by mentioning how we had no passers from deep. So we had attacking players playing out of position there with the intent of doing so, and they just moved no less horizontally than our first choice options because we still had no balance.
Anyway, I think this problem is why the club is considering offers for Sandro and Dembele. Someone on SC posted the stat that in 152 possible Prem matches since arriving at Spurs, Sandro has only played in 60 of them. Yes, he had a long term injury last year, but he only started ten this year and only made it to 90 minutes in four of them. Between him, Dembele's degrading hip, Capoue picking up long term injuries for the first time in his career, sending Holtby away, having Livermore gone at the beginning of the season, Sherwood expressing frustration in Paulinho's empathy for our cause, it provided the illusion that we were thinner as a whole than we actually were.
Therefore, we have to provide opportunities for players such as Bentaleb and Kane to blood through. With 25 players registered above the age of 21, they will all demand playing time and they will all be more difficult to appease than a 19 year old who hadn't even decided what nationality to play for at the time. We can go forward with 20 or so registered of age players, as well as foreigners below the age of 21 (a la Eriksen and Lamela last year), and still maintain sufficient strength in numbers for the extent of a season while still managing to get youngsters on the pitch.