Cybermen are probably the second most iconic DW foe, and i find the quite underdeveloped as a mob in Dalek Mod. DM 1.16 is a complete rework of the mod, so i reckon it would be the perfect opportunity to do some revamp.
Also, note that this is the first of many suggestion that have a specific monster that i would like to bring to the mod.

The mob itself in the 1.12 version is fine, but there could be some improvement. 
- First of all, i suggest to make the mob more dangerous, by having it have armor (4 armor should be fine), knockback resistance (25 - 50%) and deal more damage in both ranged and melee attacks (if it has both).
- The melee attack (especially with the Cybus Cyberman) feels a bit to basic, the the mob simply punching you, instead, to make it feel more unique and faithful to the original representation, you could have it create particles around its target (both sharpness or any custom electrical particle would be fine); furthermore, having it give a short cooldown on all items / give a very short slowness effect could increase the effect of being electrocuted and make the Cyberman itself stronger.
- Cyberleaders are just reskinned Cybermen. Giving it more health and higher attack speed could simply make it feel more of an actual threat. Also, it should spawn with 2-3 regular Cybermen around, just to make it effectively a "leader".

My second point is on "upgrade". Cybermen should be able to "upgrade" the player, simply having a chance of another Cyberman spawn in your place when you die by the hands of a Cyberman would make dying to one a very big deal. The chance with a regular Cyberman could be 25%, while a Cyberleader would have it increased up to 50%.
You have probably heard more than once of this "Cyber Upgrade block", many suggest it without actually explaining how it would work. I think it could simply increase the chance of being upgraded at death to 100% if the block is nearby. This way cyber-themed structures woulde be much more dangerous.

Lastly, after destroying redstone, Cybermats could give nearby Cybermen a buff, or increase the chance of being upgraded.

Hope you like the suggestions. I'll be back in the future with other monsters.