My Lands: Black Gem Hunting

I get rewards for quests, some army -> this is the question?
Also I get offers - buy Temple Healers for instance -> same question?

Question:
I take rewards/I buy quests, I get army, I want to take army but not all of them!!

50,000 Mercs - maybe I only want 10,000 - it makes me take and feed 50k
Similar 3,000 healers, maybe I want 100 and another 200 next week until gone - I DO NOT want 3,000 all at once today.

Why can we not choose how many reward items we take now and then more later?

Question finished, thanks for your answer

if you want 100 healers make them
if somebody told you that the right way to play is 2 years on small * ok, if you want to real game take 3k healers