‘Suppose‘ can mean let’s imagine or consider the following situation or example. For example:
Suppose they rejected an 18th-century classification system
and incorporated instead the most advanced knowledge
of human genetic diversity and unity,
that human beings cannot be categorized
It’s almost as if this imperative subordinates the whole sentence. And we are waiting for the following result clause or sentence. ‘that‘ can be used or not used.
Suppose that the variants reach a hypothetical isolated city of 1 million people
who are completely susceptible to both viruses on the same day.
that you‘re the CEO of a hotel chain
and flipping the assumptions.
In the following example, we see that ‘suppose|supposing‘ is not always the first word in the clause. Also, notice the ‘second conditional marker / hypothetical ‘were‘:
But supposing all you carpenters were to ask for more?
In the English Vocabulary Profile:
suppose/supposing (that) = C1 used to introduce an idea for someone to consider
Cambridge dictionary:
Supposing may be used with a conditional meaning. It can be used in first, second or third conditional sentences. The speaker invites the listener to imagine a situation.
A search in iWeb corpus for:
. suppose|supposing * * *
1 . SUPPOSE, FOR EXAMPLE 626
2 . SUPPOSE YOU HAVE A 462
3 . SUPPOSE YOU WANT TO 450
4 . SUPPOSE WE HAVE A 305
5 . SUPPOSE WE WANT TO 238
6 . SUPPOSE, FOR INSTANCE 152
7 . SUPPOSE, HOWEVER, 108
8 . SUPPOSE THERE IS A 106
9 . SUPPOSE YOU WANTED TO 103
10 . SUPPOSE THAT YOU HAVE 82
11 . SUPPOSE THAT YOU ARE 80
12 . SUPPOSE THAT WE HAVE 73
13 . SUPPOSE, THEN, 69
14 . SUPPOSE WE HAVE THE 69
15 . SUPPOSE I WANT TO 65
16 . SUPPOSE YOU HAD A 64
17 . SUPPOSE FURTHER THAT THE 63
18 . SUPPOSE YOU WERE TO 62
19 . SUPPOSE I HAVE A 61
20 . SUPPOSE WE WANTED TO 58
21 . SUPPOSE THAT YOU WANT 56
1 . SUPPOSING, HOWEVER, 23
2 . SUPPOSING, THEN, 17
3 . SUPPOSING A WOMAN ‘S 14
4 . SUPPOSING IT TO BE 8
5 . SUPPOSING YOU HAVE A 8