Removing old styrofoam boards between roof rafters

Hello,

We are planning to insulate our roof using blown-in insulation.
Basically, the conditions for this are ideal.

The upper floor is finished. The attic above is about 1m at the highest point "walkable/crawlable".. so far so good.

The ceiling of the top floor is insulated with polystyrene boards that are nailed between the battens.
Plan: tear them out and later install 160mm blown-in insulation between the rafters on top - that works.

But now the problem arises: the sloping ceilings down (visible from the attic) have been insulated in the same way. According to a specialist company, these must also be removed before blowing insulation (possibly with bags). The polystyrene boards cause the problem that neither can insulation be blown in, nor can the moisture absorbed by the loose insulation escape.

So the basic condition is okay, but how do I now get out the old polystyrene that is nailed between the battens down the sloping ceilings?
The length down is 3m on the north side and 4m on the south side.
Thought: remove one batten with a crowbar and the polystyrene will fall diagonally down - only works to a limited extent (blockage on the other side too strong and possibly the batten is divided).

Idea two: Build a 4m long construction and poke the stuff out until it falls down the cavity - open the roof tiles at the bottom and get it out. Problem with that: due to the narrow attic and little space above, there is little room for a 4-5m long construction to poke around.

I’m attaching a picture so you can imagine it.

Does anyone have a good idea?
Thanks in advance!

Are there two layers of EPS installed? One adjacent to the inside and the other "floating" clamped between two battens with a gap to the inside and outside? Then that is doubly unfortunate, because in the air it of course has no insulating effect at all. Anyway, if it’s hanging there in the air, it doesn’t insulate anything if the roof is ventilated from below.

I don’t see how you can cleanly get it out over 3-4m without opening the slope from the inside. Afterwards you have remnants of battens and EPS hanging around everywhere that you can’t get out, and if it is to be blown in with bags, there will be voids everywhere.

It's only one board..
On the inside facing the room, it's Heraklith. So basically also 3cm of Styrofoam/EPS but coated on both sides with wood wool and cement. Plastered on the room side (2-3cm).
The Heraklith should stay inside - otherwise I would be destroying my rooms.

So only the 3cm thick board that is "floating" nailed between each set of 4 battens should be removed.

But I see it the same way. Relatively hopeless.
And insulating there really does 0 with air above and below. I can't even explain why they planned it like this in the past or if it was just a bad idea.

Although I had an idea yesterday....
A 4m long pruning saw with a hook. It is curved and has a telescopic handle. If I slide it in from above, then by pulling on it, the boards should either be cut like butter or torn out so that they crumble downwards. This way, the roof would only need to be opened at the bottom as planned, and the crumbs/board remains could be crumbled out.