Couple of things - first I believe that there is a new (stonger) spring for the BSR and that you can take it to your dealer to have it updated. Not sure but I don' believe that there is a charge.
On the larger throat question - in the past you would have had to go to the 820 to get that. Bernina is introducing a new line on 7 series (710, 750,780) that have a larger throat - not quite as large as the 820 but I am not sure of the dimensions. Had a friend that was asking me to go look at them with her - scared that I might want one!