English Translation
I hope you will come up with a better plan.
The Japanese sentence sounds natural, but it doesn’t perfectly match the English meaning.
あなたにはもっと良い案を提案してほしい。= I want you to propose a better idea/plan.
あなたにはもっと良い案を考えてしてほしい。or 企画してほしい。= I want you to come up with a better idea/plan.
The person who comes up with an idea doesn’t need to propose it. Suppose that the speaker is the supervisor of the listener. The speaker would like to propose a new idea to the board meeting. The speaker doesn’t want the listener to directly propose it. In this case, 提案してほしい cannot be used.
案を考える（かんがえる）is “to come up with a (high-level) idea”. 案を企画する（きかくする）is “to strategize a plan (including detailed action programs)”. I prefer 企画する if it’s in a business context.