House purchase - Joint Tenants with Deed of Trust

[123NorthWest]

Looking to buy a new property with my partner. One of us will likely be providing a significant deposit - more than 50%, which they would like to be able to reclaim if we split and sell. However would prefer to own the property as joint tenants rather than tenants in common. Please does anyone know - is possible to be joint tenants yet have a deed of trust saying a larger percentage of the sale
proceeds of the house would go back to the person who contributed it if we split?
Also could such a deed of trust be updated in the future if further lump sums were paid off the mortgage by either party?
thank you

No. You can't be joint tenants and have a deed of trust. As joint tenants you each own the whole - it automatically passes to the other if one dies.
if it is the situation on the death of one of you that is the concern you would need to draw up a will saying you want your share to pass to your partner.
Yes, a deed of trust can set out what you want to happen if someone pays off a lump sum/ contributes more - then you just keep records of who has paid what.

Just to add that if you wouldn't want the other joint tenant to inherit the property, you'll have to go down the tenants in common route as you can't otherwise leave the property in your will.

Are you going to have a mortgage? The only other possible option if not is for the person who puts in more money to have a charge over the property for that amount - but that will cause a mortgage company issues so only really works with no mortgage.