Well, here's how I did it...

Install RTW. Install BI. Patch to 1.6. Make a copy of the folder so that you can use it if anything goes haywire without reinstalling...

Download the full 0.81a full installer. Install. Make sure it is working by running it. It will run on the 1.5 RTW original exe, not the BI one...

Download the Rebel CTD fix. It is to be found here: https://forums.totalwar.org/vb/showthread.php?t=81220

Then go and download all the permanent labeled fixes from this thread: https://forums.totalwar.org/vb/showthread.php?t=82256. And I mean the top three...

Now again test to see if EB loads up a campaign. Again on the RTW 1.5 exe...

Now to switch to the BI exe. Do this:
- Make a shortcut with a target line: "your install folder\RomeTW-BI.exe" -mod:eb -nm -show_err"
- Make a copy of: "your install folder\eb\data\world\maps\campaign\imperial_campaign"
- Rename that copy to "barbarian_invasion"
- Make a copy of: "your install folder\eb\data\text\imperial_campaign_regions_and_settlement_names.txt"
- Rename that copy to: "barbarian_invasion_regions_and_settlement_names.txt"
- Delete
"your install folder\eb\data\world\maps\base\map.rwm"

Run the new shortcut created above and see if all goes well...

Hope this helps...

You could also take a look at Watchman's minimod for some changes to the game using the BI.exe...