Recommendations of X2 CRT conversion

Although it seems that there are limited conversions of X2 CRT here, I am considering to have another one. X2 is much more available than others and has plenty support here in my place. Hence, I hope to get some recommendations for the conversion.
I am an Tekno Neu 1515/2.5d that is about to work with a MMM. However, I gave up my MMM because it is too risky to use the MMM even v2. I will go back to use the MM.
I would like to ask some options below:
1. 2.5d with MM and 4S (neu energy, I think.)
2. 2.5d with MM and 5S
3. get another 1Y with MM and 4S
4. others

Besides that, I will get a RCM Jammin CR motor mount, a battery tray and probably a plastic spur.
Finally, what is the gearing do you suggest?