[TF2] [Feature Request] Let mappers use custom models in Robot Destruction

[salut-c-leo]

In the Robot Destruction gamemode, robot models are managed by the tf_robot_destruction_robot_spawn entity. In Hammer, it lets you choose between several types of robots, but doesn't come with the option to choose your own models if you want to. One solution to this would be to replicate the way npc_breen or npc_alyx in Half-Life 2 lets you choose a world model in the object properties.

This QoL feature could make the gamemode more relevant in certain contexts (e.g an Halloween-themed map).

Here is how this could look like in the editor (results obtained by tweaking the fgd):

[Ashetf2]

Dupe of #3339?

[kisak-valve]

Indeed, closing as a duplicate.