There is nothing that can replace it. Not within the scope of your argument (that the unit should synergise with other the other Elite Armor abilities).
And it can't be rebalanced within realistic terms either. It has gotten a lot of QoL buffs lately and it's good enough for casual play now. There's not much more that can be done within Relic's current scope of no major changes. Similar to a unit like the B4, it will just never be competitive due to its nature.
This answer raises several concerns.
Clearly the issue of the status quo inconsistencies between AVRE and Sturmtiger balance treatment has been acknowledged by the balance team and in addition players of all skill levels have expressed discontent for the current situation. (So far I've seen 0 rational explanations for why one of the two units in identical roles is a pile of hot garbage compared to the other.)
Several fact based and easily verifiable claims have been made in this thread. These include but are not limited to:
1. AVRE reload timer oversight which makes AVRE reload cooldown start before it has even fired giving it unfair advantage.
2. The absolutely butchered AoE of the Sturmtiger makes it regularly fail to wipe squads even on 100% accurate direct hits. Especially 6 man soviet teams regularly survive a pinpoint rocket hit whereas AVRE's AoE guarantees much more reliable squad wipes even at the edges of the explosion. In addition the smaller axis squad sizes don't exactly help with them surviving but thats an issue for another day.
3. The patch notes clearly state that the reason behind the Sturmtiger adjustments was to prevent easy full squad wipes. Meanwhile collective amnesia must have occurred since AVRE to this day does the exactly same thing and that seems to be perfectly fine while AVRE's veterancy is 100% offensive instead of giving the unit gimmick vet 1 mechanics to compensate for its unreliability in its primary role.
4. Veterancy and power level disparity. As I previously mentioned the AVRE gets its power level spike at vet 1 while Sturmtiger only get's it at vet 3. Also the automatic free crit repair of the AVRE at vet 3 makes it considerably less risky to use.
5. Several smaller adjustments have been suggested in this thread and in the past that would make these units to perform in a role that would still be relevant and less cancerous. (For example a small time penalty if an AVRE shot is cancelled before firing. That would reduce the forced retreats by Axis players assuming AVRE is about to fire - something something no firing animation for a 1 shot wipe (similar to the B4 firing time penalty if the shot is cancelled mid firing animation)
6. The recent 2v2 tourney and facts available make it obvious that an AVRE is a very potent unit. So far no justification has been provided why the Sturmtiger performing in an identical role is irredeemable and is deemed to be worthy only for casual play.
So far none of these points have been properly addressed. (facts don't care about feelings)
Neither me nor the community cannot demand the balance team to provide an explanation to the status quo but the radio silence / avoiding the facts of the matter raises several theories that can be supported with the information that is currently available.
1. At one point in time the scope (tm) has failed to account for the bigger picture focusing solely on readjusting the Sturmtiger while letting the AVRE escape the nerf hammer (readjustment hammer) scot-free.
2. Double standards have been used when adjusting the Sturmtiger.
3. The community sentiment (discontent for the status quo) is not taken into account sufficiently in the balance changes. This creates concerns that balance changes are driven by feels instead of facts and community sentiment.
I hope this comment is not regarded as hostile since all the issues listed are based on facts. I can however understand why the seeming radio silence might lead to more negative backlash from the community since people might think legitimate concerns are being outright ignored.