Interesting. Do you mind to make it for every game? Also a few notes:
Pls dont check game folder anymore. Use
GetEngineVersion() instead (or even better remove that check at all in your plugin due to <tf2_stocks> is included with its extension, so plugin wont be loaded on non-tf2 game anyways).
Also there are no point of using #tryinclude <updater> unless you also add #if defined _updater_included and #endif appropriately in code. So plugin wont be compiled without that include. =\