I do expect to find more time to put up something interesting after Christmas, but in the mean-time, certain events have called some attention to Tolkien's description of the Hobbits.
Kunochan, writing at Periannath.com, statest that
Tolkien’s Middle Earth is specifically intended to be Europe in a far distant age of the past. Not like Europe, or analogous to Europe – our Europe. Its Men are the ancestors of today’s Germanic peoples, especially the Anglo-Saxons. That was Tolkien’s brief – to create an Anglo-Saxon mythology to replace the true one that is largely lost.And while this is certainly true, it also ignores some key facts about the Hobbits in particular.
(‘Of Course Hobbits Have to be White’, 2010-12-10)
Hobbits are, ‘of course, really meant to be a branch of the specifically human race’, but they are nonetheless a separate breed from the ‘Big Folk’, and so, what is known to apply to the Big Folk does not necessarily apply to Hobbits as well. The ‘Men’ of the north-west of Middle-earth may well, as Kunochan points out, be ‘the ancestors of today’s Germanic peoples’, but this, quite obviously, does not apply to the Hobbits.
Apart from more or less educated guesses about Tolkien's intention, we are therefore left with what little Tolkien actually wrote about the appearance of the Hobbits. Near the beginning of The Hobbit we learn that
Hobbits have no beards. [...]. They are inclined to be fat in the stomach; they dress in bright colours (chiefly green and yellow); wear no shoes, because their feet grow natural leathery soles and thick warm brown hair like the stuff on their heads (which is curly); have long clever brown fingers, good-natured faces, and laugh deep fruity laughs (especially after dinner, which they have twice a day when they can get it). (The Hobbit ch. 1 ‘An Unexpected Party’)Apart from information about the peculiarities of Hobbit extremities, there is little of interest here: they have brown hair and brown fingers. There is little more help to find in the sequel
[...] their feet had tough leathery soles and were clad in a thick curling hair, much like the hair of their heads, which was commonly brown. [...]; but they had long and skilful fingers and could make many other useful and comely things. Their faces were as a rule good-natured rather than beautiful, broad, bright-eyed, red-cheeked, with mouths apt to laughter, and to eating and drinking.The red cheeks is another small hint, but again it is more useful for eliminating possibilities (i.e. no black Hobbits in the Shire). The prologue also tells us that the ‘Harfoots were browner of skin, smaller, and shorter, and they were beardless and bootless’ and that the ‘Fallohides were fairer of skin and also of hair, and they were taller and slimmer than the others’ but without some indications of both the amount of variation and the average, this doesn't really tell us anything. Based on the evidence so far, we can't very well conclude anything much: Hobbits had brown hands, which suggests a brown skin, but were not darker than to be able to have red cheeks, and there were noticeable variations from this depending on breed (Harfoot, Stoor or Fallohide).
(The Lord of the Rings, Prologue, ‘1. Concerning Hobbits’)
Towards the end of The Lord of the Rings we hear about the Year of Plenty (1420 S.R.) that, ‘All the children born or begotten in that year, and there were many, were fair to see and strong, and most of them had a rich golden hair that had before been rare among hobbits.’ (LotR, book VI, ch. 9 ‘The Grey Havens’), which tells us both that golden hair had not been unheard of among Hobbits, but it had been the exception rather than the rule.
So, where does all this leave us? Not very much wiser, I'm afraid.
But that is precisely where the educated guesses take over. Culturally the Hobbits represent the rural population of the English West-Midlands about the time of the Silver Jubilee (of Queen Victoria), but the people of Dale represents culturally the Nordic countries of the sagas, and yet their prime representative, Bard the Bowman, had black hair. The irony here is that I do agree that Hobbits, apart from size and certain peculiarities about feet, hand and ears in particular, really are intended, by Tolkien, to be also physically similar to that stock of good rural Englishmen that they also represent culturally, but I think we need to acknowledge that this is just that, an educated guess, even if we do have a very high degree of confidence about it.
Praetereo censeo that it is no more problematic to have a Pakistani-looking Hobbit than to have a bearded dúnadan — while the latter actually contradicts Tolkien's explicit statements, both are, in my opinion, irrelevant deviations (I think there are things that are far more critical: the loss of an underlying spirituality in the New Line Cinema adaptations of The Lord of the Rings was, to me, far more grievous, but that is not a discussion that I have any intention of embarking on here and now).
 Humphrey Carpenter (ed), The Letters of J.R.R. Tolkien, footnote to letter #131 to Milton Waldman, late 1951?