I don't think a switch to ETH is necessary. The game would have been much more succesful if it initially started on ETH during the 2017 bubble craze but well hindsight is 20/20. As long as bitcoin transaction fees are low like right now and there is a direct on-ramp for BCY through BTC and ETH I think we are fine. What we need is more incentive to buy and trade cards and use ingame crystals. I have nearly 20 000 ingame crystals and no use? Why should I just build more and more epics which I don't need.
I think there are many easy solutions to make the game more attractive. Add new stars with new difficulty. Even 7 star campaigns are only medium difficulty. Tune it up to mythic or even genesis. Add the possibility to level cards ingame. Like if you win 100 games with a card it gets a +1 bonus on skills or stats. Add 2 new card slots for advanced campaigns. Publish the editor to create levels yourself and share them with others. Introduce new fusion cards like 2 tridents fused to one ultra trident. In order to do this you need to send 2 blockchainized tridents to a swapbot and it gives you back an ultra trident. Make it possible to farm legendaries. For example 4 quad fused epics of one element can be traded for one basic legendary of the same element. Introduce combined cards, for example if you own dark creator and satoshilite you can fuze together to get craig wright (jk lol) but you know what I mean. Add more achievements. Add harder raids with more maps and more enemies. These are all possibilities that would not take too much effort but increase endgame a lot.