Hi Roisin,
Can you share a bit about why you want to add an additional page into the ideation flow? For me that's just another opportunity for interested members to drop out. Also keep in mind that something close to the 90-9-1 rule also applies to the ideation area: Not every visitor to the ideation actually comes to submit an idea, many just want to see what is there, some of them will vote on their favorite(s) and only a very small portion actually will have a new idea to submit.
Also you might achieve what you are looking for with built in functionality already: Part of the ideation overhaul during the responsive project a new idea submission flow was introduced which adds a search for matching ideas experience. Also it includes a prominent advisory message that you can use to convey the expectations from a submission and the lifecycle an idea goes through. Take a look at the extensive documentation including screenshots here:
https://community.lithium.com/t5/Ideas/Feature-versions-Ideas/ta-p/25950
