  The present work reports on a feasibility study commissioned by the Chinese
Academy of Sciences of China to explore various possible mission options to
detect gravitational waves in space alternative to that of the eLISA/LISA
mission concept. Based on the relative merits assigned to science and
technological viability, a few representative mission options descoped from the
ALIA mission are considered. A semi-analytic Monte Carlo simulation is carried
out to understand the cosmic black hole merger histories starting from
intermediate mass black holes at high redshift as well as the possible
scientific merits of the mission options considered in probing the light seed
black holes and their coevolution with galaxies in early Universe. The study
indicates that, by choosing the armlength of the interferometer to be three
million kilometers and shifting the sensitivity floor to around one-hundredth
Hz, together with a very moderate improvement on the position noise budget,
there are certain mission options capable of exploring light seed, intermediate
mass black hole binaries at high redshift that are not readily accessible to
eLISA/LISA, and yet the technological requirements seem to within reach in the
next few decades for China.
