From the way Zhang Ansha behaved when he met Liu Zhengyun, it's very likely that Liu Zhengyun is also from the Research Institute, and holds a not insignificant position within it.
Therefore, the two options he provided are quite interesting.
First, the villa; although according to Liu Nan the villa isn't very practical, it's clear that Liu Zhengyun is quite fond of it, otherwise he wouldn't stay there every time he visits Xidu.
The fact that he is willing to offer something he loves as a thank-you gift to He Ao for saving Liu Nan twice proves how much he values this 'thank you gift'.
Otherwise, for something else worth over twenty million, he certainly has more than one; there's no need to give away something he likes.
This can be seen from the second option he offered. It's quite obvious that access to the relic is limited, and the slots are probably few, otherwise Liu Zhengyun wouldn't have emphasized that he only has one slot left.
