Yes, I didn't really doubt the developer could do it, the problems are:
1. That's not a great use of the developer's time, and
2. anything in-house increases our training and support costs
And both are completely different arguments then your original post.
1. The whole point of developer time is to save user time; if a developer can do that then it's worth it.
2. If the in-house software doesn't decrease training time or support costs then there is something wrong there.