[development] php4

Hypothetically, if a client wanted you to build a Drupal site (complexity of say, 2, where 10 is economist.com) and they insisted on a specific host -- and this host only supports php4, what would you tell them? So far I've got, -Core will work but many contribs will not (filefield, date, ubercart, etc) -Prepare for added development time that you wouldn't have to otherwise pay for -??? What would you say, hypothetically? Any official stance on php4 from d.o? Thanks, -D