Hi,

Your boss should think to the customer first. Most people don't like splash page. It is supposed to increase the bounce rate. You could do a quick test on several days to verify it.

From a pure SEO point of view, all articles I read suggest to not use it.

In my mind, only a viral splash page can rank well. I saw once on Flippa a splash page with thousands of visitors per month, but because of social sharing.

Regards,

Erwan