the only solution with no speed problems is the terminal server solution.
you should host the data in one location that has a very fast web conection and than make the terminal server availible.(you may need a server cluster)
the other version is to rent a windows server at a service provider an put all data there.
but then everybuddy as to use terminal server
there is a licence situation. (Cal per user)
look at citrix if you have more that 50 useres (more expansive but better)
another solution: if peaople only ad data to the tabel might be
let them ad the data localy and in a night job syncronice the tabel. (ceapest solution)
vpn for adding data is sometimes slow especialy if you have lookup tabels (slow)
dirk