Of course you could go to Mothercare today and buy a perfectly legal forward facing car seat for your 11mo, but the fact you've asked says to me that you're interested in the facts rather than simply what's legal/possible? This is what my thinking is on the topic anyway.
Yes, you could have a look at the Pallas seat. This style of seat seems to do better in crash testing than forward facing seats with a harness. I think the Cybex ones are better than the Joie or Jané. The idea is that the strain on the neck is less than with a harnessed FF seat because the spine curves around. However in real life crashes they do not seem to perform as well as harnessed seats (in either direction) and can even be dangerous as taller children tend to be ejected from the seat or have much more forward movement than is allowed meaning they would hit their head on other items in the car leading to head injuries which is the biggest killer in car accidents. The evidence I've seen seems to suggest they are a bit better for smaller children than they are for older ones, possibly because more of them is behind the shield part. (1yo = OK, 3yo = not good). So if you really can't RF it might be an option in the middle, but I wouldn't be comfortable using it long term, I would recommend that you look into switching to a harnessed seat, perhaps a 123 which turns into a booster seat later. Note that currently no booster shield seats have passed the more stringent R129 set of tests (the newer legislation), which may be due to the newer dummies they use in these tests which measure a bit more accurately.
The problem for me is the age of your DS. You're right that it's on a continuum and RF is safer for all ages yet we don't regularly see older children dying in crashes due to being forward facing - unfortunately at around a year of age it really is life and death even at relatively low accident speeds. When you look at pan-European data because the norm has been for many years to turn children forward facing at around 9 months you see a spike in road passenger deaths at around a year of age - this is due to a "window" of them being in forward facing car seats, which place a large amount of stress on the neck. Younger children are not dying because they are rear facing, older children are not dying (as often) because forward facing is not as risky for them. This is why the age recommendation has been changed to 15 months, although this was a compromise and many experts argued for the age to be higher. 15 months was the absolute minimum driven down by the car seat industry rather than being agreed for reasons of safety. For that reason if you can possibly make it through until the new year in rear facing - maybe by minimising car travel? I would strongly suggest you do so. Obviously it would be better to continue rear facing past this age (and it's possible that the phase will pass) but if you really must turn, 15 months would be the bare minimum for me. Then IMO around 2 is the next "milestone" - age 2 is the North American recommendation and since it's quite a bit past the first birthday it seems that the riskiest part has passed, and that's an age I always think I'd be comfortable with a child being forward facing as their regular travel mode if other factors (convenience, cost, practicality, sickness, sibling needing seat...) demanded.
Perhaps look into a good quality (Cybex or Kiddy) shield seat until age 2 and then move into a forward facing seat with harness? At this age you could also see if he is likely to last as long as you'd like in a standard, 18kg/105cm limit seat (marketed as up to 4 years, but a tall child will outgrow sooner) or whether you might need a 25kg harnessed seat such as Joie Bold, Diono Radian 5 or Maxi Cosi Beryl.
Another thought about rear facing seats is that you say you have a Stage 1 Joie seat - the belt fitted seats they do are really very reclined as rear facing options go, and you might find that something more upright is better. I know DS2 has been much happier from about 9/10m in a more upright seat in the car. Either one of the isofix spin seats which come with multiple recline options, or a 25kg Swedish style seat. However none of these are cheap so it would be a really expensive mistake if he turned out to hate it just as much. Possibly it might be an option to seek out somebody local or an ERF specialist and borrow one, or try one out for a test drive?
Lastly if you do decide to go for a forward facing seat, it might be worth looking into options on the market which try to minimise the forward movement in general in a collision. Some companies have developed some quite sophisticated systems for this now, and while they still don't compare with rear facing, they are much more protective than simply reclining a standard forward facing seat. Unfortunately (again) they are the more premium models especially as this is a newer feature in car seats, and for a lot of these your car will need top tether which you may not have.
Look at:
Britax: Advansafix / Trifix
Maxi Cosi Axissfix Air (although this is ridiculously expensive 
)
Diono Radian 5
I understand however that all of these options cost (not a small amount of) money, and if using the seat you have is the option you have, then put your efforts into making sure you've read the manual and installed it 100% correctly, and remember that a child in ANY car seat is many many times safer than a child without. We can only do our best, we can't be perfect all the time. But this is the information I'd want to have access to to make this decision.