2 draw piles for convenience?
Hypothetically, there's nothing wrong with splitting the draw pile. Splitting a randomized deck into multiple decks, won't affect the randomization. However, you need to carefully consider how you interact with the draw pile during the course of the game. 


Do cards ever get put back on top of,
into, or under the draw pile? If so,
having multiple draw piles would
affect the game. For example, if
players can put a card on top of the
draw pile, can I choose to draw from
either pile? 
What happens when the
draw pile runs out? If the normal
rule is to shuffle the discard pile
to create a new draw pile, you
probably need to wait until all draw
piles run out before doing so.  
If    you have multiple draw piles,
will    you also have multiple
discard piles?    If so, you need to
consider how you    interact with the
discard pile, also.