See? This is a great example, and a clear use for silent image.
What isn't clear is how (and if) Malleable Illusions makes it better or different in any way. I don't think it does, RAW.
For better or worse, the language of "disbelieving" isn't part of 5e. You NEED to spend an action and win an opposed check (against a DC that every spellcaster is incentivized to max out), even if you are strongly inclined to believe it is an illusion
I do think that there's a real value in a passive investigation score, so that some characters instantly see though illusions without an action. It's intimated in the PHB, but never carried through. More than anything, I think this tightens up illusion magic. With that, then Malleable Illusion can give disadvantage (-5) to that check. Which makes it a really valuable investment.
Other questions:
A. Can I use Minor Illusion to create partial cover for an archer? Normally, yes. But what if it gets created mid-combat in front of everyone? RAW, you still can -- even if you see it being formed, you need to spend an action to get see through it. Now a DM might give advantage on the check, but there's no guidance, and it still burns an attacker's turn (or else they just accept that the archer has cover).
B. Does each individual in a group have to "disbelieve"? RAW, yes. What if one does so, and tells the others. Do they automatically see through it? Some would say yes. RAW says no. Again, this would be a reason to have a passive investigation score -- being told an illusion is there gives you (passive) advantage. And the characters who dump intelligence just can't see the sailboat (
Mallrats reference).
C. And what range does examination work at? Do you need to physically interact with it? RAW, no. But at the same time, I'd like to think that being further than 30' (say) makes it harder to see through an illusion.
As I've said elsewhere, a half page of guidance could clear all illusion magic, and make it somethign that rewards creativity but leads to predictable responses from a DM, which simply isn't the case right now.