Certainly, it could be a more polite request to say
'If you will/would wait here,…’
if you’re a receptionist who needs to left a customer for some time to arrange something with other staff.
But wouldn’t it be ‘extra-polite’ (= sarcastic) if used in informal ‘peer’ communication? For example, among colleagues.
(Just to note: it’s a usual and general problem for foreigners to be polite ‘adequately’ – not too much, not inadvertently rude. Just sufficiently.)
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With a colleague or acquaintance, both are too formal, really. Something like Sit here a minute, OK? would do.
Being overly formal, however, is better than being underly so, and is certainly not necessarily seen as sarcasm or disrespect-- these are shown more in tone of voice and behaviour.
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Thank you, Mister Micawber.
You’re right. Of course, ‘Sit here a minute, OK?’ would be better…
Unfortunately, in some situations and with some people (even colleagues) there is a need to be a bit formal… 
But not ‘too much’. 
That’s right.
But it reminded me the classic “only-after-you” situation - with two men before a door, when they both try to surpass each other in politeness.
Also I’ve heard the English expression I will if you will