rc1985 - I can offer some general thoughts. The 1988 CS1.2 is a worthy speaker, having our first copper shunting rings on the woofer and our first aluminum tweeter (with ferro-fluid). Its development paralleled the 1989 CS5 and shared technology development between those co-products. I consider the CS1.2 as definitely worthy of up-grade.
Your woofers are from Vifa and have rubber surrounds. Foam went out with the original 'O' series. The surrounds should be renewable with rubber rejuvenator. I suggest you contact Rob Gillum at CoherentSource Service for recommendations.
I have done work on the successor CS1.5, but not yet on the 1.2. I am willing to get XO information and make recommendations. However, I will caution that replacing XO components is a rather expensive route to higher performance. We might rather look at other low-hanging fruit of port aerodynamics, grille-board attachment, wire, terminals, XO placement and signal routing. We can wade in via PM if you wish.