You actually have a problem with a USF player trying get anything he can out of a lategame? I sure don't. IMO with how it stands now (no heavies for USF), the "extended popcap" is a feature not an exploit.
Any player should try to get anything out of any game phase. That's part of a competitive play style.
There is a restriction, tough. All kind of unfair play is never an option and using game mechanics in an unintended is unfair play. The weaker late game is part of the US faction design. Its something a player has to deal with. This is a disadvantage that is compensated by a stronger early and mid game. In case such a desgin dessicsion leads to game breaking balance issues, something i fail to see by the way, then it´s up to Relic to alter this design.
To be honest i am a bit shocked about your opinion. Do you remember about the On Me exploit and how CoH2.org reacted to people using this in exploit in their stream? Thats the reaction i was expecting.