Could you please help and explain to me how to correct the seemingly incorrect passive voice sentence pattern?

Solution 1:

The statement is ungrammatical, and needs 'seated' if an active, punctive usage is required. 'Seat [someone etc]' is transitive; 'sit' is usually intransitive (and therefore resists/disallows passivisation). But then 'I would prefer it if we could sit next to a window' would be far more idiomatic.

However, there is a possibility that the stative, durative sense

• 'I would prefer it if we could be sitting next to a window [when the rest of the party arrives, say].' is the intended sense. 'The following is an extract from an article by Patricia T. O’Conner and Stewart Kellerman in Grammarphobia:

We were sat … or were we? December 1, 2017

Q: Do all British people say “sat” instead of “sitting,” as in this example from a Brit’s blog: “We were sat around the coffee table”?

A: No, not all British people would say something like “We were sat around the coffee table.” That usage isn’t considered standard English in either the UK or the US.

However, quite a few people in the UK do indeed use “sat” that way, and the usage shows up once in a while in the US too.

In an Oct. 3, 2012, post on the Oxford Dictionaries blog, the lexicographer Catherine Soanes notes the increasing nonstandard use of the past participles “sat” and “stood” for the present participles “sitting” and “standing” in British English.

She reports hearing several instances of the usage on the BBC, including “She’s sat at the table eating breakfast” and “we were stood at the bar waiting to be served.”

Soames, editor or co-editor of several Oxford dictionaries, says the use of “sat” and “stood” for “sitting” and “standing” in continuous, or progressive, tenses is “regarded as non-standard by usage guides.”

So in this case also, the choice of 'could be sat' is non-standard.