freebsd internal

[cisco Baz]

to whom it may concernim going to make  a freebsd  such that it can act as a web url filtering gateway but i dont want use tools such as dansguardian or squidguard or ... tools that use proxy to implement url web filtering , also dont want to use firewall package in freebsd such as pf , i want to write a program such as pf but such that can filter based on layer 7 information but independent of other package even if needed change kernel , ... 

so can you please help me a little  ?
best regards