comma delimited column fix
The view could do something like this (obviously I've guessed at table/column names):

CREATE VIEW dbo.whatever
AS
  SELECT src.columns /*...*/ , IDList = STUFF((SELECT ',' + CONVERT(VARCHAR(12), p.ID)
    FROM dbo.ProperRelationalTable AS p
    WHERE p.EntityID = src.EntityID
    FOR XML PATH(''), TYPE).value('.[1]', 'nvarchar(max)'), 1, 1, '')
  FROM dbo.SourceTable AS src;


However as @Martin pointed out in a comment, this view will break the application if it expects to perform any DML against the view rather than the base tables. You can avert this problem by setting up INSTEAD OF triggers as he explained.

A related post that might be useful in other ways aside from just the presentation aspect:

http://www.mssqltips.com/sqlservertip/2074/make-your-sql-server-database-changes-backward-compatible-when-changing-a-relationship/