Oh yes! I never actually played The Sims Medieval, but I would definitely be interested in a new version if it was sandbox - or perhaps even a historical based simulation game with different packs inspired by different time periods. Then there's also the idea of a Lord of the Rings / medieval fantasy pack with dragons, orcs, elves etc. for those that like that sort of thing. The possibilities are endless. I am an 'old soul' who swoons over period dramas and a total history nerd though so I may be in the minority. I remember I loved the Victorian and Versailles based stuff packs for TS3, but then the cars and phones would kind of shatter the fantasy.
