It's difficult to pinpoint the issue exactly since something actually could be wrong in the process.

But well I can't say I tried to do the thing you have attempted. Have you looked at the Spiritual Freedom and edited the various things related to that?

Have you then examined the autospells like thunderstorm and tried to work around that to not be entirely be dependent on a start of the battle mechanisms?

Can't give you any advice other than that

So the exact effect I was looking for is the possibility to have a starting magic effect for a tactical duration I can choose myself- but I have already changed the design since then as it's not working currently, despite linking to a magic effect.
By the way (but this is more than a quick fix), being able to redirect to a targeter would have been even better in terms of flexibility and the vast field of applications which could be done with it.

I do believe it's a very very quick fix in terms of code to make the start of battle unit property to works correctly with the duration setup in magic effect, and for the possibility to link it to a targeter... well, for Aow 4 ? ^^

Most likely. Missing alot of crucial things not available.

One thing I miss is a 50% modifier on damage to total health. I would be happy to create that kind of spells. But the game crashes even doe it works. Engine is not happy about negativa heal on % when health reaches 1 hp