I don't know if it requires an engine modification or not, but I think that throwing grenades over the obstacles like walls, small buildings, etc. would make a lot of sense. This way "Throwing" would make a valuable additional skill for any combat-oriented character.
Of course it would require the ability to throw/shot directly to the ground (without having to aim at the target, since it's not visible behind obstacles), just like in F:Tactics, which may (or may not) be difficult to implement, but it's logical.
That's my little suggestion

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Thanks for reading.