I have developed a mature big application ( 200 installations in last 5 years) that is based on VPF native tables. Most of the business rules are on the form level. Most of the insert, update, and retrieve of data are based on SQL commands. I do not use views at all.

Lately some of my customers require to transfer the date into SQL database, for good reasons: security, huge tables (millions of records), remote access etc.

I have two options:

a) Copy the existing project into a NEW project and modify the existing application to work only with SQL databases.

b) Modify the existing application on the logic:
if lsqlmode
new code for sqldatabase
else
the oldcode
endif

What option should I choose?
Is the second option realistic?