Glad to hear you liked my idea. Here is several more ideas -
1. Yes, gambling can be good idea. Many people like this. But the games need to be good enough. For lottery, it will be weekly(mainly), daily(for decent no. of regular users), hourly(only if you get many active users). People will receive 1 free lottery for every 2,5 or 10 claims in caves (your choice), 1 for every 1000 hashes (or your choice) mining, or buy lottery.

2. About Free Roll - You can associate it with level up. For beginners e.g. level 1-3, they can claim highest times (your choice like 15/20/24 times a day). Each claim will give some xp. They will get Cash+MCC but it will be lower. If they level up higher, the reward will be increased and no. of claim decreased.

3. If you think the Free Roll will be complicated like this, then introduce 'Daily Bonus'/'Loyalty Bonus'. I think I don't need to explain this. Reward will be in MCC/Cash.(Cryptomininggame is a good example for this). Even you can have both these features.

4. About CPU Mining - It's currently upgrade based but the initial rate is very low. As you have said, "Sadly it is noticeable that people are losing interest after a couple of clicks, and we don't want it to happen", how can you expect people to use miner? You should rethink about it. I suggest to add Cash+MCC
here also. Cash may be fixed, MCC will be upgraded like now.

5. Have a facebook group and promote your site. Have weekly promo codes (valid till 24 hours), arrange contests like referral contest, most claim(improving current one), most hashes mined etc.

6. Unlimited offline miners can be bad later. Few high level people can abuse it later if they want. I think you should reconstruct this section (not necessary right now).

7. Add multicoins payout to faucethub (If possible).

These are completely my thinking. Others may or may not agree. But these are the things I think you can work on.