Don't use the editor either, I used a batch to mass convert all the .dat.adm files to .dat files in the extracted pak copy; editor just slows me down for the vast majority of TL modding
It's possible, but would probably require a lot more editing than preferred - there's a workaround where you can create a hidden 2 lvl skill, have it do nothing at lvl1 and have it as a 'passive' that causes a summon (most likely via a loop that just resummons it every so often) at lvl2, then the item can just have a +1 lvl to that skill. Having that skill do what you want should be easy enough - you have the shadow armour effect as a base and merely need to replace what is actually summoned with Alric's dragon, it's just triggering it to activate only while the item is equipped that is a little more tricky, hence the workaround. All this is possible with a standard mod, it's just triggering it to activate and deactivate at the right time that may take a little work, and of course adding a skill to a character hurts compatibility with other mods and limits the usefulness of this. Be certain the skill is hidden if you have to use an infinite loop to keep it summoned, background processing might be ok with infinite loops (provided each loop cancels the previous before reapplying the effect so it doesn't eat more and more memory each loop), but the UI most certainly won't be.