What about the other option of first attempting to make Egypt our trading partner? Where would that be addressed? Can we not try per-turn deals on tech & workers? This way, we guarantee a return on investment (i.e. the tech), rather than Egypt's help in the war (help that is not guaranteed). After dealing, I think any civ would then be less likely to join the larger conspiracy.
In the case that we can & do per-turn deals, if Egypt declares war on us, we are no longer committed to paying the sum.