You could either define it in the GUI globally somewhere and then pass it to every GuiInterface call, or just make it a member of the GuiInterface directly. The Engine.PickSimilarPlayerEntities method does not exist in the simulation scripting context, but the same thing can be achieved through the GetEntitiesByPlayer method combined some additional manual checks. That would also allow filtering entities by the "Tower" class instead of their template names (as you mentioned in the comment), if wanted. By the way, the GUI already caches entity states (in g_EntityStates).

When I tried to do so, it gave me errors, telling me rustc is too old. I read later in that thread that I need to install rustup, but there was no instructions for it. Ideas?

I only have sufficient time on weekends. Also it actually seemed like the time was a bit too early in fact  Possibly i could do round 2 this weekend, but i dont know yet wether i will have time.

UPDATE: Version 0.10.0 - Added retail trade - Added transfer of coins to deposit with subsequent income - Statistics for retail trade and deposit - Update interval for retail trade and deposit 5 seconds - Barter Multiplier changed to 1.0 for all resources - Income from units and buildings has been reduced by 2 times.   Retail Trade: When you right-click on a resource “for sale,” it will be transferred to retail and sold in small batches, but at a more favorable rate. If this resource is Coins, it will be transferred to a deposit and the player will receive interest on the total amount. When you right-click on a resource “for buy”, it will be transferred from retail back to the player. Min amount = 100