The tower system is mentioned at least on Crosswind Kite Power with Tower which is a concept studied by @floba , and for the cosine loss reasons you mention.
However, in this chapter it is shown that tethering the kite to the top of a tower instead of to the ground can have advantages: Most notably, the “cosine loss” is reduced, i.e. the misalignment of the wind velocity vector and the direction of the traction power transfer.
My opinion: a train of parasails aiming to reach several hundred meters of altitude or even more than a thousand meters as mentioned in the poster that you and I cited, will only be raised to the height of the tower. Said tower will undergo cantilever efforts. That’s a lot of inconvenience for minimal benefit.
True, but a parachute flying horizontally is not more a parasail (so a sort of parachute kite) which has also lift in addition to drag in order to rise. And rising is needed in order to reach more consistent and powerful high altitude winds.