Personally, I believe that, living us in a heavily interconnected and globalized world, every action that is relevant on the political field should be based upon a "global mindset". Local narratives seem a thing of the past. What's the point of saving Lewisham Hospital without reclaiming global right to free health? Helping migrants in the Mediterranean Sea shouldn't be based upon a feeling of pietas, rather this action must be intended as a battle on the field of reclaiming global citizenship. "Papiers pour tous!" was the slogan of 1996 Sans Papier in France. 

I think that creating bridges between people is the best way to fight contemporary world alienation. I guess, people that frame life from a Marxist prospective (I refer here mainly to class struggle) often do not realize how those that are exploited everyday do not constitute an homogenous group. Rather, the proletariat is characterized by differences and stratifications. Exploitive labor can be waged (as in the case of the invisible cleaners), some can be not (as in the case of non-productive labor such as reproductive labor). It can have a fixed number of hours per week; contrary, it can expand to fill the entire life of someone. Having said that, I totally love Anna's first idea:

"1) Seeing/acknowledging:

For the duration of the project we acknowledge people that are normally 'invisible', specifically on campus, because as I have said in our meeting I find it that it is where people, especially cleaners are invisible the most.
This might be as simple as a nod, making eye contact, saying "thank you", or just treating them like any other person, not pretending that they are not there, or we could take it a step further and actually have an action that acknowledges their contribution: a party, a talk etc. not sure.
"We call ourselves the Invisibles," say the University of London Cleaners."

Putting ourselves in the position to understand in a radical way what being an Invisibles means gives us the right prospective to melt our political demands with the demands of those that are too part of those who are exploited but are not exploited in the same way. Living under the constant threat of debts (as in the case of student loan) is not the same thing as being excluded by society due a specific job. There are differences, of course, but these differences vanished when placed in the large picture of global capital exploitation. Even if conditions of different pieces of proletariat seem different, they are the result of the same global mechanisms.

Hence, arranging an actions that directly involve us and "invisibles" seems a very smart idea to me.