Malzahar or Yorick Rework Idea
I actually started thinking of this idea because of the Malzahar rework that had been announced recently and I honestly would like to see this on Malz, but I realize that it ultimately could work better on Yorick because it really seems almost too similar to how his kit works now.
The biggest difference in this kit from Malz's is that it summons different voidlings per ability instead of with his passive and I'm not sure how it would work to do this and maintain the effects he has now, which Riot has said they would like to do with at least some of his abilities. The reason why I don't see this working as well with the way Yorick's ghouls work currently is that they die too quickly. If they lived about as long as Malzahar's voidlings this could work better. Also, Yorick's passive would need to be adjusted because there would most likely be more than 4 ghouls fairly regularly.
One of the other major focuses for this idea is to make each of the 3 voidlings have different strengths that scale on different stats. I personally enjoy playing AD Malz and I am really hoping that the rework does not take that away. The three voidlings/ghouls are Melee/fighter, Tank/bruiser, Range/mage.
Fighter
These melee voidlings/ghouls would deal physical damage that scales on the champion's AD stats and would have an attack speed that scales on the champion's CDR. They would have low HP and by default, lower cooldown timers than the other minions. I would set not limit on how many of these can be spawned, but I would think that full CDR would allow for about 4 to be summoned at once.
The idea for maximizing this playstyle would be to build AD and enough/or CDR to swarm your enemy with hard and fast hitting minions. These would provide a strong front line to harass and press the enemy while a weaker back line offers some protection to the champion. The major drawback to this playstyle would be that mana would quickly become a problem.
Tank
Only 1 of these voidlings/ghouls can be summoned at a time and he has a much longer lifespan than the others. He would also have a melee range, but would have significantly more HP and resistances that scale with the champions respective stats. This guy would be much more protective than the other two, and he would stay within a much closer range. He also becomes stronger as the champion becomes weaker, dealing an additional 2% of his bonus damage per 1% of the champion's missing health.
I see this working best with a tank build so the champion is able to maintain a lower current health without as much risk of dying. Even without tank stats, this provides some additional safety. The problem with this playstyle would be that you would need to rely on your single voidling to deal most of it's damage while you have low health. Your other minions would not be strong enough to do much more than provide supporting harassment.
Range
These voidlings/ghouls will attempt to stay behind or to the side of the champion offering little to no protection from forward skill shots. As the name suggests they will have a ranged attack that scales on the champion's ability power and applies some form of effect, such as a slow or magic pen. I would say these should have a limit of 2, maybe 3.
I believe the AP build would still be the strongest. Your fighter minions would still do a fair job of providing long range harassment and your tank can still attempt to block poke for you.
Passive idea: Malzahar I am throwing this in after I have already typed all of the voidling ideas because it occurred to me that this would completely negate his passive. So I had an idea for how to keep it the way it is, while still using the different voidlings. The voidling summoned could be determined by which ability was used last, or 4th. Instead of summoning only 1 voidling per 4 abilities it would summon up to the maximum for that type.
Another idea would be to simply make his passive to be able to freely summon any one voidling if there are no voidlings alive currently, and the use of this passive can only happen once every XX seconds.
As I said before, this would probably be best as a Yorick rework, but I really like Malzahar better. Maybe this could even be an idea for a new champion. I have no idea what the rework for the ultimate for each champion or Yorick's passive would be changed to. I really think Yorick's ultimate should be something completely different as well, but that is just my opinion.