Expedition: general discussions.

There are no other default actions that a character could perform (say, try to push an opponent to another position) or creative uses of abilities with vague wording (say, use magic to turn a piece of a stone column into mud and collapse the ceiling).

In principle, this sounds interesting, but the downside is that the GM will often have to determine the mechanics of such things on the fly. For example, the column and ceiling should have a certain number of hit points, and the mage needs to inflict enough damage with his mud magic for his action to work. The number of hit points will have to be invented on the spot. I personally like this, but won't there be complaints later in the thread that some ceiling was too strong and couldn't be collapsed in one turn?
Automatic success of any "creative" action is also not an option.
Kicking into the abyss, by the way, can also be considered not particularly creative and can be introduced into the system in any case. Only it is better to prescribe such a possibility in advance (for example, accuracy check against agility + strength against resistance => successfully kicked), otherwise someone will kick one of us and there will be complaints again. And even better to make corresponding skills for pushing, I am a big fan of that.

So, in conclusion, it's not entirely clear. It's up to you. I would try to anticipate such possibilities in advance
(for example, in the description of the mud beam, I would write that it is possible to destroy objects with a mass of no more than X, etc.)