Its about management.
Regardless of the fact that the requirement for web development skills comes from your department, this resource should be placed within the team best capabable of managing their skills and the project(s) on which they are working.
It is likely that the team/department manager who looks after 'analytical software development' will be running a structure more suited to the requirements gathering and development process, and will have progress reporting procedures in place to ensure that the developer is using their time effectively.
Furthermore, when your site is complete, and is entering the maintenance phase, the software development group is best placed to:
1) Ensure that the skills for maintaining the site are transferred and shared within a team of competent developers.
2) Ensure that the project is effectively documented.
3) Identify other projects where this developer skills may be applied.
In short, Yes - you are being power hungry - unless you have considerable experience in manageing software development teams, leave development to the group assigned to this work and use them as a service to you.
