Interpreting これからもAしてBしよう Does and apply to both or just to B? Example: > Does it mean > Alright, let's keep specializing in defense and playing! [We've been already doing both.] or > Alright, let's specialize in defense and keep playing! [We've been already playing, but didn't specialize in defense until now.] Or something else entirely?

I think this is adverbially modifying . That is, it says "to play it specializing in defense" or "to play with a dedicated defensive style", not "to specialize in defense _and then_ play". Therefore applies to both as a set. The sentence means "Let's keep playing [it] with a dedicated defensive style!"

Remember that te-form can explain how the second action is done:

*
to go to school on foot
(Not: to walk and then go to school)
*
to cut paper with a knife
(Not: to use a knife and then cut paper)



See: form and adverbial meaning