We played a game with the Operations Expert, Celebrity Activist, Quarantine Specialist and the Field Operative (and the purple disease). Initial hotzone dice rolls were pretty tame -- mostly good sides, the outbreak one, and two towers on different locations. The problem is that the above combination pretty much negated the hotzone dice. The OE was able to negate the Towers pretty much every turn, the QS was able to move wherever we needed her, and because of the OE, we pretty re-rolled any pure travel faces that came up, resulting in a lot of $ and Treats for the CA and lots of Treats for the QS. And of course we have the FO re-roll for as many sample containers as possible.
Anyway, basically we kept outbreaks to a minimum, so that face of the hotzone dice was irrelevant, the OE made the Towers irrelevant (usually had 3 bases in play every turn), and the splat/rate side only came up once, and even that was not a threat because we were able to prevent most outbreaks and it switches to evacuation.
So I thought I would throw out some ideas for variants to increase the chance they will become relevant to the game in scenarios like above.
First one is when placing an epidemic's hotzone die, the player must re-roll all hotzone dice already present in that region.
Another idea is to re-roll *all* already places hotzone dice when an epidemic occurs, though that sounds like it would be too hard when playing with roles with few if any free movement.
Another could be that when placing a base the OE has to re-roll any hotzone dice in that region.