My goodness, what have you done? This beast is growing faster than a biter nest. The Smart Train Combinator version is just one more step in its evolution.

I'm loving it even more every time.

The next step could be to add the foundry to a logistics network with buffer chest style actions. It could have the ability to set a default level of supplies by the user based on a logistics group so it could be set/changed from any logistics group compatible entity, and a second hidden unnamed group where the foundry requests what ever is needed above default levels for any print it is told to build. Activate the trash unrequested feature and everything refunded from recycled trains is added to what's needed for future builds or automatically moved my logi bots into the logistics network for reuse elsewhere.

Doing the same thing with the other version makes building trains to the Smart Combinator descriptions even easier.

Of course, until they research the logistic bots they'd still need to use inserters to add/remove stuff. It does not need to be tied to the logistic network research since the rocket silo works the same way. Though you might need to be careful with prototype usage since it would suck to loose the Logistic network embargo achievement from placing something with a hidden buffer chest in it.

Thanks for your comments.

I thought about integration of a blue chest at start from the first version but I prefer a simple chest.
As you say, only the rocket have logic network integration, and look like more natural to just have inserter like all other manufacturer.
The combinator give signals of request or stocks. I enlarged chest size to be able to have a arm as input and an other for output.

In my game I myself and a blue chest reading the request else fuel and a convoyeur bring the fuel. I think it's better to give choice to user like that.

Next updates in my mind is to use the v2.1 and choice cable color to have the request signal and content at same time.
And I'm really not proud about the extension... Hard to place... I'll make do something automatic like just "add extension" button

Rather than adding extensions could you add an option for max train length before it's built? They are only building one per surface so the extra step of typing a number when building it shouldn't be to much work for the aspiring engineer. Oil planner and mine planners both have 'setup' GUI before you 'draw' the ore field.

you mean choose like 15 for the size and the mod place enought foundry for the size ?

Sure. You could make it work in steps of 4 or 5 as needed. So if you have it designed for 5 car sizes and they pick 12 you build for 15. A simple note in the prompt would cover any 'surprises'. Or, if it's something you could work out in the graphics, maybe build it exactly for the requested size.

nice idea but I like to make it evol after the fist placement and paying the extension as the cost of the first foundry