I tried playing many other video games which attempted to replace Master or orion/magic and they all seemed to have failed. I tried Age of wonders, heroes of might and magic, and galactic civilisation and they all seem to have missed their target. After analysing master of magic/orion's game design I have realised that what makes this game unique and addictive is the fact that the spells and technologies are very powerful.
For example, galactic civilization you devellop tons of technologies where 1/3 of them only has the purpose of letting you accessing other technologies and the other technologies gives meaningless bonus like +10% to hit in combat. This has the effect of making tech development boring and almost useless. What does it changes if you have +10% to hit, it won't gives me a that much interesting edge over my ennemy which I try to overcome.
In master of orion, technologies has important impacts over the game which increase the need to develop certain technologies and gives you access to some "punch-through" elements to overcome your ennemy. Many times in MOO, I refused to trade some technologies because that would have mean giving an advantage to another player who could become my ennemy or who could trade it around to other players.
Now about elemental, from what I have heard, there is a technology system split in different fields that you can upgrade and eventually gain bonus to production and other things. This is fine, as long that it is not the primary technology system. The structure is fine as well, it does not give you tomsof tech to learn and there is no tree to analyse.
In a game like master of magic, the primary technology system are the spell. This is the elements that should be very powerful in the game. What makes MOM fun is that the players have a feeling of power and control over the game. There are other games like age of wonders which does not give you this feeling because the spells are too weak.
Also, the fact that MOM takes place in the whole world, rather than a portion of the world |(like in age of wonders) also gives a feeling of superiority when you actually cast a spell which can affect the whole world.
So in overall, if your tech system gives bonus here and there, it's OK. But make sure your spell gives more than bonus, like breaking rules, allowing new actions, OR give really considerable powerful bonus.
It's OK to have a progression, at the beginning the game, the spells whould not be that powerfull. But at the end you should have spell powerful enought to give you a weight in negociation with other players (ex: if you don't stop attacking me, I cast armageddon). You can also increase the area of effect rather than the effect. Ex: Flame Sword: Gives a +3 damage to a unit. Later on, you can enchant all units in battle and near the end all units in the world.