Like you say there are no weight restrictions for licences, looks like that changed when JAR-FCL came in.
So yes a PPL could get a 747 Type-Rating, requirements being 70 hrs PIC, hold or have held a Multi-Engine IR, completed the ATPL theory and hold a MCC certificate. FCL.720.A refers.
Because you need the ATPL Theory, you might as well do the CPL skills test otherwise your ATPL's would lapse and wouldn't be able to do another type rating unless you resit all the exams. That is should you eve want to exchange your 747 for something smaller.....