This is not going to bring a solution to the problem you're trying to fix.
1. As long as you have a way to replace planes with new planes and instant delivery of used planes the problem will be there. By adding time to when the plane can be replaced you'll only reduce the range of used planes condition at which they would be useful to be bought and not solve the issue at hand. That however is not that much of a problem as is right now, as most people do not replace planes at extremely low condition to begin with.
2. Adding "refurbishing" will not change anything, as players can manually order new planes and replace the old ones once they arrive, then sell the old ones. What the "refurbishing" thing will do though is add unnecessary micromanagement and tediousness.
There are 2 possible solutions to this problem, one along the logic you;re using - namely, add the "build duration" for new planes to the "replace" functionality. Basically every time you replace a plane, it does not happen right away as is now, instead an order is placed as if a new plane was ordered and the replacement happens after the plane arrives. This will add some load and computation I'm sure.
The other way is simply to put a "wait time" of x weeks for used planes to arrive after purchase.
In the end the used plane market is used to gain access to planes "on the spot" and start using them on routes right away and the replacement is secondary.
1. "By adding time to when the plane can be replaced you'll only reduce the range of used planes condition at which they would be useful to be bought and not solve the issue at hand." <- i think it will still be useful to buy 2nd hand airplane? For example u get a condition 45% one, and u have auto-renewal at 50%, say construction time is 16 weeks. Then i will still use that 45% airplane for 16 weeks until my re-ordering of the new airplane replace it at the 16th week? It is still useful if i want an airplane NOW. If i want better condition, i can refurbish it a bit? The problem i try to solve is that an airline can get a brand new 100% RIGHT the way at any time. So i think this fixes the problem?
2. "That however is not that much of a problem as is right now, as most people do not replace planes at extremely low condition to begin with." <- This might not be an issue for airlines that do not use that exploit. By I DO lol. I get always get an instant 100% airplane right the way if i spend a bit more money (very little bit more, like 20% perhaps?) I think this is just NOT right
3. "Adding "refurbishing" will not change anything, as players can manually order new planes and replace the old ones once they arrive, then sell the old ones. What the "refurbishing" thing will do though is add unnecessary micromanagement and tediousness." <- I think what you said is correct. I am just trying to cater to some smaller airlines that can afford 2nd hand airplane only (and don't want to wait) and make the airplane slightly better. I do agree that it could be micromanagement in some sense as people might come back and do it repeatedly (my design is to only allow to go back to X% based on age Y, and at some point of age, refurbish is no longer useful anymore and the airplane would have to retire)
4. "Basically every time you replace a plane, it does not happen right away as is now, instead an order is placed as if a new plane was ordered and the replacement happens after the plane arrives. This will add some load and computation I'm sure." <- ya a possible solution, but it requires changes to data structure and model (and possibly UI too, to mark when will the airplane be replaced). Think i will just stick with the "auto-renewal" option for now
instead of giving a more mico-version of it. You can argue that the "auto-renewal" thing could be a cheat too. Cause if u change it to a lower threshold, you will get ALL the airplanes u purchased before cycle X renewed, which is not right - as you did NOT place a replacement order before that. However, it still solves the problem of instant-buy-2nd-hand-and-replace.
5. "The other way is simply to put a "wait time" of x weeks for used planes to arrive after purchase." <- not for now. People are already getting annoyed about the construction time. I don't want to put more hurdles on buying off the 2nd hand market. It will really **** people off if they want to increase capacity but cannot do it right the way even from the 2nd hand market.
Thanks for the suggestions again! I think I kinda lean towards removing the "replace" option from the airplane completely now and only allow auto-renewal with the "purchased cycle" check