The problem is that you are imagining the number of bananas using a one dimensionally structured number line constructed by your mind that represents one meaning, the number of bananas. Intuiting i bananas (or intuiting why "i bananas" can't be imagined) requires understanding that our concept of numbers is already multidimensional in the realm of meaning.

Imagine first that your mental construct for bananas only went 1,2,3...

Adding a zero as a concept helps with accounting of bananas by extending the scope of your construct to include the absence of any bananas. You can now communicate and record not just a sum of bananas when you have them but a lack of bananas when you don't. But you can't actually imagine zero bananas. To imagine zero bananas, you have to juxtapose that against the concept of 1 banana. You have to know what a banana is to know what 0 bananas isn't. It's not the same as zero apples. There is another dimension of meaning. When you imagine zero bananas, you are imagining the empty void or lack of one or more bananas. Otherwise you would be imagining zero. 0 bananas are different than the numerical symbol 0. 0 bananas is a 2 dimensional representation of bananas, that does not fit on a one dimensional number line. Likewise 2i is different than "2i bananas."

Negative numbers as a concept helps with borrowing and lending of bananas by extending the scope of your construct to include a dimension of ownership, obligation, and debt. While you might currently hold the mental construct ... -3, -2, -1, 0, 1, 2, 3 ... consider that this is just a symbolic representation of the real world. While you might be able to slide back and forth along this construct with numbers in your imagination, crossing the 0 doesn't equate to sliding or exchanging bananas, it equates to an entirely different real world concept, your obligation to provide a banana. Or your banana debt. Or someone's banana debt. You can't actually imagine having -1 bananas. You can't imagine -1 bananas. What you can imagine is owing someone 1 banana. Or having one less banana. Or someone being in debt to someone one banana. The continuous number-line has within it a hidden dimension of meaning that we just happen to hold in our minds as a continuous construct representing a single meaning. -1 is not -1 banana. -1 banana is not 1 banana. -1 bananas is a 3 dimensional construct. Transactional relationship direction, value, object.

Now, for imaginary numbers and imaginary bananas, we have to realize that the same holds true. 2i is not 2i bananas. You can't have -2i bananas. You can't owe someone -2i bananas. You can't imagine having, possessing, or trading -2i bananas. You can't be in debt for -2i bananas. But, by extending our representation of bananas into a 4th dimension of meaning we can do complex transactions/manipulations with our bananas that would otherwise be impossible in three dimensions of meaning. Imagine being indebted to someone for 25 bananas. You are obligated to pay them X number of days per week for X weeks. X*X = 25. So you imagine 25 bananas on a square grid. You know this is a 5x5 square but how? You have -25 bananas and you can't squareroot a negative. Can you even imagine a grid that is -5 by -5? Well, obviously, what you're really doing is imagining a 5x5 grid, and taking the transactional relationships as a separate dimension. That's how i works. 2i bananas means nothing by itself. It can't be imagined. But in a larger context, it does mean something. i can be used to represent an additional dimension of meaning. A meaning that I've vastly oversimplified here, because it doesn't really translate to bananas, but it was the closest I could figure out how to get.

i by itself doesn't really mean anything other than the square root of negative one. And the square root of negative one doesn't really mean anything by itself. But in a larger context, it allows us to expand the computations we do into another meaning space.