The problem is general migration and asylum seekers are talked about as if they are the same thing. Most migrants are primarily "economic migrants" or people who move for love or family and apply for work, family visas etc ahead of time and outside of the UK. Maybe there are too many economic migrants, maybe there are too few. But if we drastically reduced it our prisons would face staffing issues and we might have to release murderers etc (oh wait!) and people would be sad their American husband couldn't come and live with them.
Asylum seekers (people who are in the process of applying for refuge) and refugees (approved including people who got here 50 years ago) are a much much smaller group. In total they are 0.7% of the population. Asylum seekers whose claims are being processed are a fraction of that 0.7% and the ones with no legitimate claim are a fraction of that. Which is still a lot if you are trying to find accomodation for people while their claims are being processed. But they are not the reason for any demographic changes people might see and like/dislike. Neither is it an invasion. We already have quite robust standards for rejecting people falsely claiming asylum. (I guess that's what you mean when you say economic migrants being processed). However, for a long time no-one was actually sent back because the last government (Tories) had a stated plan to "deter" people by not processing their claims. This just meant the numbers of people waiting built up and up. It did not deter anyone. Even though Jenrick painted over that children's mural.
I agree we need to process claims and send back people with no right to stay. The problem is a large proportion of people applying have legitimate claims, they aren't tempted here by the luxurious conditions in migrant housing and aren't economic migrants. The conditions in the hotels are probably a bit worse than the average homeless hostel which are also bleak. They are living where they have been told to live by the government. You can't apply for asylum outside of the UK so everyone that does it has to get to the UK first and then apply. This isn't the same thing as being "illegal" or cheating the system. They are following the rules of the system as it exists.
I don't know what housing people on remote islands would do for "deterrence". For one thing, there are already people living in Scottish islands and if a hotel of migrants in a city is such a disaster** I don't think housing all the asylum seekers in tents on winter in an area with 100 local people is better? If nothing else, it's going to be annoying for the Scottish crofter to keep tripping over the frozen bodies of children and adults on a winter morning. The current plans to house migrants away from urban areas on former army bases is giving the far right reasons to demonstrate so why would they be OK with Scottish rural areas? Unless it's just a fuck the Scots thing.
Also how bad do you want it to be for the deterrence to work? I guess your description of tents/portacabins on northern Scottish island = bad but I don't want to put words in your mouth by calling it a concentration camp. But... it sounds like a concentration camp. The worst case scenario for these kinds of plans is you have people forced into very poor living conditions. And then we can point to the consequences of these poor conditions (cramp anyone into a very small space and restrict food and you will see worsening mental health, suicides, an inability to keep the area clean because the infrastructure isn't there to remove waste, criminality because ummm they are freezing to death) and say "see these people are bad". And it is also counterproductive as presumably when someone is granted asylum they will struggle more having lived in a concentration death camp for five years.
I completely get the frustration when people with legitimate concerns about migration are labelled racist. But can't you see how "put them all in tents in freezing Scottish islands, that'll learn em for fleeing war" opens one to legitimate criticism?
**I lived near one with no problems and without realising it existed. I appreciate other people have had other experiences.