Well, it turns out Egosoft made one, and it just isn't available when you first start playing X4.
With version 1.1.0, I added a trade start that should look quite familiar to X3 players.
Install Instructions:
1. Download the .rar file
2. Extract the "TradeStart" directory into "Path\To\X4 Foundations\extensions" (create the "extensions" folder if it doesn't exist)
3. Start the game, select 'New Game', and you should see the new gamestarts
Download link:
v1.1.0 - https://drive.google.com/open?id=15wksh ... -OK6fIaVYj
v1.0.0 - https://drive.google.com/open?id=13iJqR ... fk8L_F41Q1
Changelog:
2018-12-01 - v1.1.0 - Added an trade start that should feel very familiar for X3 vets. Use v1.0.0 if you just want to unlock the Egosoft X4 trader start.
2018-11-30 - v1.0.0 - Initial release, removes achievement requirement from the Egosoft designed Trade start for X4