Converting a bone to a mesh or poly shudn't affect the hierarchy, but i repeat, i don't think it would work. In the best case your bone will be considered as a model and become visible in-game, or it may be badly interpreted and screw your animations. So you have to make a new bone, place it the same way (with aligh tool)…
I fixed the bone problem and didn't get an error, but now the weapon is way out of place in-game, I can't even see it. It also has no texture, but it is visible. (model viewer)
When trying to export a view model reference, I get the following error: Writing Meshes... * "bip_hand_R" WARNING: Could not get a material for mesh "bip_hand_R". Skipping mesh. Assign a Standard or Multi/Sub-Object type material to it. bip_hand_R is a bone, why would it need a material? On a semi-unrelated matter, are…
Ahem... If you've done that then you need to make sure your vmt and vtf files are set up correctly and in the right spot. As for the modeling being way off, if you exported without it skinned to a bone, then it is using the objects local pivot which is probably way off in the distance. You should reset it on the hierarchy…