I think one of the most important factor for miners is: to calculate how much is the risk to mine bigger blocks which other miners will accept and mine on top of it.
Coinbase Text in BUIP005 only shows what size miners want to mine, but doesn't show at what size he will accept it right away and mining on top of it.
So I would suggest to replace the "Maximum Generate Size" with "Maximum Acceptance Size (AS)" Combining with the Proposed Activation Block Height (ABH), this will indicate miner willing to accept and mine on top of any block that not bigger than AS after ABH. This is for the coinbase text only, not for the user-agent, and miner does't need to show the Excessive Block Size.
Knowing how big the block that other miners will accept is much more useful information than how much they start to produce.
Coinbase Text in BUIP005 only shows what size miners want to mine, but doesn't show at what size he will accept it right away and mining on top of it.
So I would suggest to replace the "Maximum Generate Size" with "Maximum Acceptance Size (AS)" Combining with the Proposed Activation Block Height (ABH), this will indicate miner willing to accept and mine on top of any block that not bigger than AS after ABH. This is for the coinbase text only, not for the user-agent, and miner does't need to show the Excessive Block Size.
Knowing how big the block that other miners will accept is much more useful information than how much they start to produce.