This idea is something I had considered as well. Personally, i like the idea a lot as it adds another dimension to the field which is aways good- more variables adds to more avenues of play.
It would have to be "costed out" properly but it is essentially an early investment for later rewards. Since the improvements or negatives (assuming you could plague your opponents field slots" would be permanent they should be quite costly in sp.
For instance, we have magic weapon which provides 1 unit with + 20 attack (permanent) for a sp cost of 1. Therefore, it stands to reason that if you had say a card that modified position 1 on your battle grid for attack (insert number here) then it should cost more so that it doesn't replace cards we have in addition to it being a recurring effect. I suppose you could place time limits on them as well ( next 2 or 3 turns etc.)
I think Goscar is correct that the idea is sound it would just have to be implemented correctly.
I would really like us to get end skills in Alteil Horizons. Just my personal wish list.
What do you think about adding seasons? Not sure what effect you could do with it but what if say turns 1-7 was summer, then 8-14 was autumn, 15-21 was winter and 22-30 spring? It could be overkill and we already have night/day like Worthing said but it was something that crossed my mind a few times. Plus, I like Sakon.
Nought's had, all's spent, Where our desire is got without content;'Tis safer to be that which we destroy Than by destruction dwell in doubtful joy.