I want to address two problems here:

- The time to complete a hero is getting bigger and bigger, and we are bombarded non-stop with more and more new heroes, sign in hero, vip hero, event hero, so we have more and more heroes that we don't play with -if they don't make it to "meta" it is not worth spending on them, (alternatively, if we had one of those non-meta heroes fully max trained and max geared we might be able to use them from time to time in real places - the thing is that we don't have that, because we don't invest anything on those heroes. So we never use those heroes).

- I am a little bit worried that releasing new and new heroes, especially the vip ones, make the difference between vip and non vip bigger and bigger, and it is shame to see people quit because of that.

So there, a couple of ideas for new content (since you are releasing new content and new features anyway), this should be joined to a slow down of release of heroes (for example, if a month has an event hero, I would not release any vip hero - or put the event hero in the rewards of signing in of next month - with an extra of soul stones- and therefore you avoid releasing any shitty sign in hero...):

1. Feature "challenge quests"

That would be pretty much like the 3rd quest on the legendary quests. Things like a. "complete chapter 17.3 with only this hero". b. "complete chapter x with all heroes alive" c. "complete this chapter while hero x dealing xxx damage". d "complete chapter x while hero x dealing the last hit". e "complete chapter x with less than x time" f. "complete chapter x while all of your heroes have more than 50% remaining hp". g "complete chapter X while having max energy on all your heroes" h. "make this hero deal at least xxxx damage in raid? "

Those challenges would be open for all heroes. You first choose the challenge, and then you chose the hero. When you successfully complete a challenge the reward would be training cards specifically for the hero that you've chosen. So you can spend some time making non-meta heroes stronger, and having fun with them.

I would apply the vip system in 1 of the two following ways:
1. Opening new level of difficulty for the challenge (just the same challenge but for the next campaign chapter), so vip players receive more training cards (still the max would be the max lvl training on the campaign, so at the end non-vip and vip would have the same result, just vip players would reach there faster)
2. First I would limit this feature to be able to be done just twice per day (one per each hero, you can repeat hero if you want). Then according to your vip level, you can have more times to attempt the challenge. (Still unsure if it should be attempts, or completed attempts)

2. Give us more dragon pearls!

I was about to think of something else, but it all boils down to just getting more dragon pearls! You can think of any feature, just the reward should be at least 20 fragments of dragon pearl...

Ok I stop day dreaming.