I understand. Not that it's relevant here, but I'm pretty sure a current Gold could do a Plat challenge.

OP - how far are you flying in these 4-5 trips per year? If most of the flights are fairly long, especially if you're making connections, you might be able to get Gold status with the Citi Executive card plus the flights.

It's not hard to make Gold if you fly internationally or even transcon flights. It is a lot of flying if you fly a lot of short-haul flights mixed with some mid-cons and live in a hub (like me) but you might not be too far depending on your travel patterns.