Upgrading Air Units Realistic?

[explorer2]

I'm working on modding WaW, looking at historical values, etc...

It occurred to me that fighters (and bombers for that matter) weren't ever significantly changed from production. When new and better designs came out, they were produced from scratch. Older ones stayed in service as long as possible. For instance, the entirety of the carrier air of the Royal Navy in 1939 were still biplanes.

This is a game, not reality, so what would be the advantages and disadvantages of making it so that air units in WaW could not be upgraded?

Thanks in advance for the input.

[SSFSX17]

None of the upgrades are realistic, even the rifle infantry upgrades, since their increased hitpoints would indicate that they were re-trained. I guess it depends on whether or not you want to represent the full difficulty of modernizing your armed forces in the middle of a war.

[Barthheart]

This is a good point and one I've thought about before as well.

Maybe do it this way using fighters as an example:

1. FTR I avaiable at start.
2. Research FTR II. These cost a bit more than FTR I. FTR I still available to be built but can't become FTR II.
3. Research FTR III. These cost a bit more than FTR II. FTR II still available to be built but can't become FTR III. FTR I becomes unavailable.
4. Research FTR IV. These cost a bit more than FTR III. FTR III still available to be built but can't become FTR IV. FTR II becomes unavailable.

Same for tanks, ships.

Infantry types could still be upgraded. Should cost a lot in supplies. Also let one step down be available when the new one come available. This could simulate cheat second line troops for garrisons etc.

It all depends on what you want the "upgrade" to represent... retraining, new equipment....

[bebert]

Actually, upgrade system works well. You can upgrade subformation one by one if you want, but if you produce more PP than supply, you will not have sufficient supply to upgrade all your subformation in all your unit - in fact, more unit you have, more difficult is to upgrade all your units and subformations. You will have to make choice, and you will have young and modern unit that have to stay training at rear, elite unit with a lot of experience that you can upgrade with supply, but that you can not reinforce massively if you want to conserve the unit experience, and you can conserve some middle class unit that you upgrade or not.
 
I think this system is réalistic. Upgrade simulates the technical progress, new weapon, may be new and more efficient combat doctrine, but not training. Experience simulate training.
 
But, if you modify item type, you can conserve production of old model and units if you want. But I don't think its a good idea, if the cost of new units is the same than old one. But you can modify a little bit the cost of the new one in the sftype or itemtype, it could be a solution.Tiger II was more powerfull but more expensive than tiger I.