… if somehow we can set the database Alias to ADO connection …
Just take a look at the source code of Delphi’s BDE and ADO support (in e.g. DBTables.Pas and ADOInt.Pas + ADODB.Pas and you will soon see that they are as different as chalk and cheese.
You have no hope of e.g. using a TAdoConnection via the BDE from a Delphi app.
What you could do is do move your data to an ADO database (e.g. MS Sql Server) and then create a) a System DSN to connect to the ADO db via ODBC and then b) set up a BDE Alias that uses the BDE alias and c) change your existing BDE app to use the new alias instead of the one it currently uses. That way, you can continue using your existing app to access the ADO version of the data via TTable, TQuery etc and develop a parallel TAdo-component based equivalent at your leisure.
You could easily try this out using the traditional Delphi MastApp or “Fish Facts” demo application and data. Getting your existing BDE app to access an ADO-compatible copy of your data via an ODBC alias should not be more than a day’s work even if you have never done it before. Actually converting your BDE app to ADO would likely take rather longer, though.
There are countless examples of different ways of copying BDE (e.g. Paradox) data to ADO data on the internet. Try looking at a few.
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solved BDE to ADO conversion in DELPHI 5