I'm assuming you're doing the approvals through a task list? If so, you could just run the approval process through the existing list by creating an approval choice field (approved/denied) and creating a custom workflow in SP Designer to look at the approval field and act accordingly. This would allow the end user to approve the item on the submission form. Alternately you could enable content types and create a content type specifically for approvals with the approval field on it. This would be more for instances when your end user is submitting the item for someone else's approval.
UPDATE: How to embed ID in URL link for approval email:
Click on an existing item in the list and copy the URL. You can also copy the URL in the edit form if you want the item to automatically open in that form. If you are using content types and have a specific form for approvals you can also open it in that form so that it pulls up specifically the form they need and in the content type they need it in. When you are in SP Designer building the email you can insert that hyperlink into the body of the email. Edit the hyperlink and in the string editor find the part of the URL which has the ID (for example: EditForm.aspx?ID=56). Highlight the ID number, in this case 56 and insert a lookup value (button at the bottom left). Select the ID for the current item. It'll now link them back to the item the workflow fired on and open in the desired form so that they can quickly update the item.
-- The current item ID is related to the workflow item ID not to the task ID... it usually match (if one task is created by every workflow) but could be easily desynchronized.