AMO allows for unlisted add-ons that just get auto-scanned for obvious problems and then signed immediately. That's the preferred method for cases like yours.
Alternatively, you could run Nightly (or an unbranded build[1]) and disable add-on signing, although that opens you up to having _any_ unsigned add-on installed, not just your own.
Alternatively, you could run Nightly (or an unbranded build[1]) and disable add-on signing, although that opens you up to having _any_ unsigned add-on installed, not just your own.
[1] https://wiki.mozilla.org/Add-ons/Extension_Signing#Unbranded...