Avoid the aggrevation of Aggregation using Numpy .... from this blog post
and to avoid repeating myself... and just halve the cell size when bringing back into arcmap
a
array([[0, 1, 2],
[3, 4, 5],
[6, 7, 8]])
np.repeat(np.repeat(a, 2, axis=0), 2, axis=1)
array([[0, 0, 1, 1, 2, 2],
[0, 0, 1, 1, 2, 2],
[3, 3, 4, 4, 5, 5],
[3, 3, 4, 4, 5, 5],
[6, 6, 7, 7, 8, 8],
[6, 6, 7, 7, 8, 8]])