Hi,
First, great job on this version, i expect it would make it playable in early game without killing the base idea !

Some thoughts on the GUI:
-- Overhaul tab --:
- The values calculations should be based on settings, not "80%"
--> If i set "100" for replacement age in settings, i have "80%", "+25% scrap", "-25% break" on GUI, which doesn't seem right. Should be "100%", "0", "0".
--> As settings allow from 10 to 1000, i would expect the horizontal scrollbar to allow same range of values
--> What about "i don't want to replace this type" possibility ? (maybe when cursor is at full right ?) Note it's only a question, i don't have any real use for this.
--> Maybe change setting text from "minimum age to request replacement" to "Default minimum age [...]"

-- General --
--> Maybe nicer to use the bottom quickbar icons rather than extra top button, as i believe it's made for such things ? This is getting crowded on top left with all other mods xD

It looks great anyway, i'm definitely giving it a try !

Wow, thank you for your feedback and suggestions! Your ideas sound neat. I'll do the following:
- If the default replacement age in settings is changed, the replacement age for all machines that used the previous default value will be updated (e.g. if you change it from "80" to "100", only machines with previous value "80" will be updated to the new default)
- The replacement setting will be limited to 300. I've never experienced a machine older than 220, so this should be enough.
- The slider will be changed to allow all values from 10 to 150 in steps of 10, from 150 to 250 in steps of 25 and the second to last value will be 300. If the slider is dragged to max, this will show "no replacement" as value.
- The description and name of the "minimum age to request replacement" will be updated

I'll also think about your suggestion to add a quickbar icon to acces the GUI, but this is of lower priority right now.

I think 300 is definitely enough, especially with "no replacement" option.
Can't wait to actually deep test this, but Wint... i mean Weekend is coming :)

Is there a difference between removing a maintenance item using the menu and simply not delivering it? Eg, if I can't make lubricant yet, am I better off turning off lubricant as a maintenance item or does it not matter?

It does not matter in terms of additional aging, but if you have a bot network, it avoids the "missing construction materials" alert for this kind of item.

It works like the following: A machine keeps track of two lists. The first one contains all items and amounts a machine requests for a specific maintenance (or repair) event. The second one only contains those items from the first list that are allowed for use via the maintenance control settings of this force. Only the items in the second list will be displayed in the maintenance request alert sign. If you disable all items, then the second list will be empty and the maintenance alert sign won't be shown at all. Regardless of this, the background logic continues as usual: After some time it checks how many items have been delivered in relation to the first list.

The mentioned changes have been implemented in the latest update