First off, I hope you've joined the "IHG® Business Rewards", it can potentially nett you alot of points as a corporate booking decisionmaker. Feasable for your particular situation or not, you need to investigate.

Secondly, im not sure about your friends/colleagues, but room upgrades are subject to the member's room only. And If I were you I would be bugged by the inconsistency of upgrade policy they are enforcing.

You should leverage your power as a valuable client (since you bring them so much business) , by talking about your negative upgrade experiences to someone with power (E.G Director of Sales to write an official email to reservation/frontdesk staff). (etc. loved the upgrade i was getting and proposed to my company to sign corporate rates, but now unhappy that not getting upgrade as plat at least for my own rooms)

Lastly, i've made it a habit to ALWAYS check my app for the next category and next next category room (from the one that i booked) before checking in anywhere. This has been my saving grace a couple of times, for example when i called out the frontdesk staff when she said that all suites were full for the Crowne Plaza Singapore, showed her the app that suites were available. And suddenly she said that a suite is free