is there any way to increase unit experience from the scripts
With the Esf Editor you can change unit XP within a saved game. With the PFM you can make a mod that will give your units a higher starting XP when recruited.
There used to be a way to edit unit experience for the pre-placed units that the campaign starts with. Could even add/remove preplaced units/generals etc. However, the last time i edited any such file, it was for rome total war. I'm unsure if those files would be the same for ntw.
I'll have a look and report back if i see anything.
RTW game files are great. You can get in there and change soooo much stuff.
how can Build Unlimted DLC Unit
You might be able to do it with the PackFileManager, search at TotalWarCenter.
how can Build Unlimted DLC Unit
It's no problem, just edit the newest patch-file with PackFileManager.