I simply opened the original Megaton Walkway with the GECK and corrected a NavMesh issue.
Permissions and credits
Credits and distribution permission
Other user's assetsSome assets in this file belong to other authors. You will need to seek permission from these authors before you can use their assets
Upload permissionYou are not allowed to upload this file to other sites under any circumstances
Modification permissionYou must get permission from me before you are allowed to modify my files to improve it
Conversion permissionYou are not allowed to convert this file to work on other games under any circumstances
Asset use permissionYou must get permission from me before you are allowed to use any of the assets in this file
Asset use permission in mods/files that are being soldYou are not allowed to use assets from this file in any mods/files that are being sold, for money, on Steam Workshop or other platforms
Asset use permission in mods/files that earn donation pointsYou must get permission to earn Donation Points for your mods if they use my assets
Author notes
This author has not provided any additional notes regarding file permissions
Fallout should be updated to the latest patch to avoid problems in general
Via FOMM, NMM, or Mod Organizer: Everything follows the basic procedure for all files. Manually: Again, follow standard procedure for all files: drop the file in the Data folder.
Warnings/Troubleshooting/Things to Know
I made this long before I knew much of anything about modding with the CK, let alone the GECK, so no promises I didn't really mess something up, but I've gotten no problems from commenters so far (and it's been over 2 years so I doubt I did). To that end, I'm not sure if Fallout 3 had preferred navmesh pathing as Skyrim does, so more often than not the NPCs won't use the bridge themselves. It breaks immersion a bit, but it's mostly a convenience mod anyway.
Any warning that applied to the original Megaton Walkway still applies here.