Simplicity is, of course, subjective. The argument presented seems to be balanced but is this merely because we're projecting our own expectations and experience? What would my dad make of a form asking him to "re-register for the new site"? Dunno. But a phone call to a relative may well be involved...

Naturally you know that when you say "much simpler" you implicitly add "with respect to all the requirements I'm balancing". Beware what the development team and business analysts are implicitly adding - they may not see your solution as "much simpler"!

Finding that appropriate balance of requirements requires that an appropriate weight be given to each viewpoint. Additionally, the social role of an architect requires that appropriate language be used for each.