You can create descendant of TSQLQuery where you can override virtual method GetFieldClass() and return own TField descendant which will handle AsDateTime in a special way
(you can create own TSqliteFloatField = class(FloatField) ... define there GetAsDateTime and use this new field type for REAL columns (ftFloat))
For usage you can look at fpjsondataset.
This week I am kinda busy, but next I have some more time. This hint will be very useful I am sure.
Thanks