Korg Poly800/EX800 Users

I was looking at the schematics and trying to understand the FM-800 mod. So I gather that the Osc 1 is routed to P 19 - VCF Cutoff Lin In for FM.

This got me thinking that we could use another pin for amplitude modulation using DCO2, e.g.:

IC 5 - P 7 routed to either:

1. NJM2609 P 9 - VCA Level CV Lin In (risk of feedback here?)
2. NJM2609 P 2 - Mixer Signal 1 Level CV In

2 seems much more fun to me as then, DCO2 could Amp Mod DCO1, which itself routes to the FM Mod.

Is there any additional parts needed than resistors and a suitable potentiometer here?

This would make for some electric piano sounds or more types of sound effects as in those examples:

http://www.propellerheads.se/substance/discovering-reason/index.cfm?fuseaction=get_article&article=part20

Your thoughts?