This is my understanding of the situation.
Home Grown (Association)
1 John Stones
2 Kyle Walker
3 Fabian Delph
4 Raheem 'The Killer' Sterling
Foreign
1 Vincent Kompany
2 Aymeric Laporte
3 Nico Otamendi
4 Danilo
5 Ben Mendy
6 Ferna
7 Jorginho*
8 David Silva
9 Bernardo Silva
10 Kevin De Bruyne
11 Leroy Sane
12 Riyad Mahrez*
13 Sergio Aguero
14 Gabriel Jesus
15 Ilkay Gundogan
16 Ederson
17 Claudio Bravo
*or whoever we sign, foreign or association trained will still take these slot.
B List
1 Phil Foden
2 Aro Muric - will be club trained on January 1st
3 Brahim Diaz - assuming he doesn't go out on loan.
4 Plenty of other players who are unlikely to actually see game time (The Nmechas and Duhaney etc) but we'll still register because there is no limit and in the event of a catastrophic injury crisis we could use them.
We could free up another foreign slot if absolutely necessary by selling Bravo but that would require us to make some interesting squad decisions. Muric could be our backup goalkeeper from January 1st as he would take one of our unused Home Grown (Club) slots but until then we would still have to have a minimum of 2 in the senior squad (ie: not B list).
We could use Gunn for this slot but I think that's probably unrealistic because he will likely want first team football, either in the Premier League or Championship - heard Leeds were sniffing around but I reckon he'll stay at Norwich if he doesn't move up. The only realistic way of doing it then is by registering Daniel Grimshaw as he is already club trained, but then that raises questions of whether either Muric or Grimshaw is actually good enough to be our backup, plays the right way etc etc. So its extremely unlikely we sign a third player this summer for me. In January maybe if Pep really rates Aro but for the time being unless Bravo or anyone else leaves I don't see it happening.