I'm going to re-reply to this because it could be a one time thing. Right before you join a world you could set it so it could be default or at any time. If a server chooses default avatars, stay default, or put in conditions where only specific models are supplied, such as server provided ones. If servers want to add Elves, Orcs, and anything they should have the ability to let players choose. That is, unless it conflicts with the main character system.
Unfortunately this would result in a few problems. Even if servers can decide to enable/disable this feature, it would still be confusing for a new player (I guess most new players who join a server wouldn't pay much attention whether or not this setting is enabled on the server). On the other hand, if a player is able to select a custom player model and joins a server which does not have this feature enabled, he wouldn't understand why he suddenly has the default player model.
This feature could result in a lot of unrealistic and unnatural player model... for example, player 1 uses the default player model, player 2 is just a cube, player 3 decided to use a mini-scaled model of the USS Enterprise, player 4 plays as a giant phallus etc. This motley mix is certainly suitable in other games, but I'm afraid that does not apply to Rising World 
But even from a technical point of view, this would introduce a lot of problems: Our clothes wouldn't be compatible with custom models (unless a player sets up proper bone weightings for the model, but even then, what happens to player models like the mini Enterprise?). Hitboxes would also be tricky...
Another issue would be the amount of triangles of a custom model: Most players probably tend to upload a high poly model (since a character with 10M triangles looks much better compared to a model with only 10k triangles), which would have a huge impact on the performance. It might work in games like VRChat or Tower Unite, since they don't have to render such a complex world, but in RW, we need these resources to render the world and the player buildings. If we put a cap on the max triangle count instead, I already see some negative reviews incoming from players who are frustrated that 9 out of 10 models could not be used in RW...
I admit, such a feature sounds interesting at first, but it wouldn't work well in a game like Rising World 
If we add it as a modding feature instead, the server admin is responsible to use proper models (in this case, he has a lot more control over that since players wouldn't be able to upload their own models).
Out of curiosity will there be a way to shrink the size of the heads of display when opening the crafting menu with the new version?
Well, the UI will have a completely new design (we will get rid of the fully opaque wood design), and instead of using absolute sizes, the new UI will scale automatically depending on your resolution. If you're using a resolution lower than 1080p now, the current UI elements will be extremely large (covering almost the whole screen). This will definitely change with the new version 
