Squads available (For lieutenants) are....

Squad 4 (Medical Squad) 
Squads 8, 9 and 10 all of which have no particular role 
And as riddle says squad 12 (Research + Development) still has a lieutenant place available :) 

Either that or 3rd seats are available on almost every squad bar 2, 4 +13

Looking forward to your Shinigami! And don't worry as this is a completely non-cannon RP there shouldn't be any spoilers. I think the only place that would happen would be the Skype chat if we all begin to reminisce :P but since you don't use skype that shouldn't be a worry. Welcome to the RP!