FYI, see the article "The Curse and Blessings of Dynamic SQL" by Erland Sommarskog, SQL Server MVP at

http://www.sommarskog.se/dynamic_sql.html

To workaround the the size limitation, one approach is to use views. As the dynamic SQL uses the view, it is often simplier, easier to debug and is often shorter than the 4000 character length restriction of sp_executesql