Hi. How about the following suggestion:
1. Keep the axefactory as upgradable from the metalwork shop, AND
2. Add the option to build the axefactory directly.
Since (in build 16) you can already upgrade the metalwork shop immediately after building it, this does not affect game balance. But it does remove an unnecessary micromanagement hassle for the player that wants to build an axefactory and not a metalwork shop.
As it is (build 16), if you want to build an axefactory, you have to watch the metalwork shop like a hawk and upgrade immediately after completion, or else your workers will load up the shop with precious raw materials that you will lose when you upgrade. (I don't imagine that this micromanagement hassle is intended as part of the game balance, but I may be wrong)
This would still allow players like SirVer to build the metalwork shop first, then upgrade. And it would make it easier for players who want an axefactory first (or want multiple axefactories and only one metalwork shop, or prefer to play without metalwork shops, etc.)