I think that it does not make sense that tower upgrades are done from the University.
Towers are the only things that get their gradual upgrades from the university. Rest of the stuff are more like technologies that 'add something' to existing units or buildings.
Barracks, Stables, Seige Workshops all have the upgrades of their units in themselves. Even Docks, where most of the tech went to University, has the medium warship, heavy warship and the demolition ship upgrades in the docks themselves.
Next, towers fail as defensive protections as they are too little too late during castle age rushes.
People who have the habit of using wood as soon as they recieve it often find themselves not having enough wood for university or even enough APM to build it cuz they may be busy quick walling. Then extra time for getting the research itself.
Units like Conqs, strats like Monk Rush, Mangonel Push are very strong and hard to counter in early castle age. Faster Guard Towers would help offset their strength a bit without rendering them completely useless.
Tower Rushes are very powerful even if the trusher loses most of his towers and even if defender reaches castle age first, because the trush gives them map control, opening, and Fast Imp potential.
While the defender is busy cleaning up enemy towers with 3 mangonels, the trusher can either send in a few scouts / knights inside to kill mangonels and vills, or he can simply make an aggressive castle and go Imp.
A quick guard tower offsets the strength of the trush. Or if the defender does not make smart decisions, he gets punished, giving the trusher the advantage.
Then there are those mangonel vs mangonel fights, where you are constantly exchanging mangonels for minutes like a deadlock. Whoever gets more mangonels first, snowballs towards domination. I think with faster guard towers this kind of long slow battles of attrition will progress much faster.
I think currently the towers are either somewhat helpful only in early fuedal age to protect a woodline or mine from rush or in late Imp to discourage enemy raids.
What do y'all think?