How about having a 10x10 Espionage board where the board setup looks like this:

xxxxxxx---
xxxxxx----
xxxxx-----
xxxx-----y
xxx-----yy
xx-----yyy
x-----yyyy
-----yyyyy
----yyyyyy
---yyyyyyy

The 28 X's represent Black and the 28 Y's represent white. The way different setup can change the strategy of play using the same Espionage rules (but removing a 1 and 2 soldier from the original 30 pieces). And of course, no one says you have to put the main base in the corner!