The most challenging part of having a blade enclosure system like HP c7000 blade encloure series is the getting the firmware to match the components. For example, you may start off with BL460c G7 blades and 1 year down the road decide to add Gen8 blades into the same enclosure. It is not a simple question of just plugging them in, many times it will not work as the underlyin OA firmware may not support Gen8 blades. However, one cannot just go ahead and upgrade the OA firmware without first checking the firmware versions of the G7 blades and iLOs to ensure that the new firmware is supported by each other. This is usually not too big a problem when the blades are new and estate is small, but if you have them deployed globally and over a few years, you can be assured that firmware versions will be very varied. And any attempts to standardize just say the OA firmware can difficult.
This is why HP has a compatibility matrix for its system. It used be a bit more complex (but easier) as the table would state the minimum firmware version for each component to work with each other. So you may want to upgrade the OA firmware to 3 versions higher but keep the rest the same, it would be not an issue. However, they have since streamlined this and force everyone to upgrade to a single version level. So if you want to upgrade the OA firmware to 3 version upwards, you need to upgrade all other components to the same version base.
Now if you are runnning ESXi hosts on these blades, your have to consider recommended driver versions which works in tandem with the OS version and the HP blade firmware.