So basically you're switching all your SPS and assets from the main account back to the original account? Well I would do the same if it were me. Modern is where the excitement and better rewards are. So will you rent out the cards, or just let it be?
I used to play with two accounts (modern and modern) and after the release of the Arcana set one in modern and one in wild.
Now I will only play with my main account in Modern and Survival. Playing with two accounts, one in Modern and one in the Wild made sense because this way I had 100 energy points instead of 50. I verified that playing in the Wild with 70K SPS does not produce significant results and therefore it is better that I play in Modern and Survival only with my main account which will have almost 140K SPS = a higher SPS boost ;)