Satoshi set the decimal point by taking the total number of units and sticking a decimal point in the middle. (21 000 000.000 000 00)
Or you can see it is four sets of four digits, equally arranged around the decimal point (2100 0000.0000 0000)
I have not dived into the technicallities, but if that is correct, it should be rather easy to split the BTC, and make a btc into 1/00 210 000.000 000 00 and thus make the effective market cap(in units) 100 times higher and still keep it as BTC units. One "unconverted" BTC would simply be an OBTC (original bitcoin) that was split into 100 BTCv3 or BTC for short. (add a version per decimal place)
As long as the community is agrees on such a change, I don't see any reason why it could not be done. This would most likely increase the market cap, as having a coin that is worth 1-2 USD seems less confusing than one that is worth $100-200. For users and miners the only difference would be that instead of 1 BTC, there would be 100 in the wallet, and the blocks would be 2500 BTCv3.
In-fact this have been done several times with FIATs and are frequently done with stocks to have more manageable units. Although with FIATs it's normally the other way around. (Like when 10.000 polish zloty became 1 new zloty)
Erh... Seems like I totally misunderstood and thought that 1BTC was coded as 10 000 000. 000 000 00 - Oh well.