I think they underestimated the number of Japanese fans (and others!) who would want practice tickets... despite the local French fans who we spoke to, who
tried to warn them. And the tour company buying en masse is just bad form.
They ran out of gala practice tickets the day we bought ours (actually, the "tickets" are nice plastic cards, the size of a credit card - nice souvenirs!)... and lucky us, a fresh batch arrived just as we reached the head of the queue. I think they're making them onsite...
Yes, I looked into various stadium seats and similar "devices", but none of them looked like they would fit/work with the Marseille seats :-/ Or they looked too flimsy, or too bulky (we travel light, hand-luggage only...)
There are indeed no rails down the steps... so yes, you have to wonder about who they did/didn't design the place for.
By the way, I have to say the event is being organised better than I expected (!) - there have been some gaffes but at least they seem to learn from them and not repeat them each day. Clearout after practices and re-entry with competition tickets has been quite quick and efficient.
I have been astonished at various "ladies" who sneaked into gold seats that weren't theirs... and they knew it... but then argued and fought endlessly when challenged by the rightful owners and the security guys

One had to be bodily removed. Why do they waste everybody's time (including their own), and cause so much disruption, when they always end up forced to move anyway? Do they really think they can win, and
stay in somebody else's seat?!
Bringing your own food/drink is indeed banned, I discovered today. I got lucky and the few things I had in my bag the last couple of days went undetected - but it appears others (most?) have not been so lucky. Well, at least there is a café, and a well-stocked kiosk selling (quite palatable!) sandwiches, salads, fresh fruit, panini, drinks etc. I won't take any chances on the remaining days...!
They've been letting hordes of schoolkids watch the practices from the upper-level seats, yesterday and today. Not sure what they were like today, really... but I am pleased to report that yesterday's kids seemed impressed and were really getting into it - cheering enthusiastically for the big Pairs throw jumps, twists and lifts etc etc...