That's just crazy . But I think your idea could work
Ok so a few questions before I try evaluating the card.
1) Are the transformed minions yours to use? If not then you are basically going to use this card as "removal" which is not that good.
2) Why did you design this card? What is its purpose and what possible synergies could you create?
3) Don't you think 5 mana for an effect that is not always consistent and doesn't clear the board is a lot?
I'm going to try to suggest some changes based on what I know so far.
1) Increase the stats and cost. Something like 6 mana 0/5 should do. You might think Its a lot but bare with me I will explain it later on.
2) Add another effect. Rush is nice however it needs something more to give you an advantage. For example, Infiltrate: Rush, Provoke (going to be insane if you have a lot of minions) OR Grow +1/+0. Here is why you need extra health and a higher cost. If you want provoke then you want more health and 6 mana because you can ruin your opponent plans easily. Now Grow is not as good since your opponent will get the buff first.
3) The rush exist so that you can move around and transform minions. Yet that by it self is not good enough. Maybe you want to use it with cards such as Frostfire, Wind Sister Maia etc If you want Wailing Overdrive and Aspect of the Mountain it cant cost 4 or more. So consider changing something else. If that is your goal then I don't recommend adding more abilities as I said in #2. What you should do in this situation is to lower the cost to 4.
So far cant say anything else because I dont understand exactly what you are trying to accomplish. Think about what I wrote, answer my questions and I will help you