You might be able to use group policy for installing off-web-store extensions -
If not, there is no way other than extracting the CRX and loading it as an unpacked extension, which is going to warn you on browser startup - every time, yes.
This is a security measure, a lot of malware used Chrome extensions without user consent (by adding them to the Preferences file, for example), so they eliminated this way for good. You cannot say, "this is fine", because this approval must be kept somewhere and malware will just use that place to override any extension blockage they want. Sorry.