I am researching the help-to-buy ISA scheme. The average variable rate is set on 2% for most banks, however some banks offer extra but they put a further condition on it that you cannot hold an additional cash ISA which I believe is what is referred to as an "split ISA". Most banks offer it, but a few banks forbid it and instead offer an increased rate. Now my question is:
Can I open a Htb ISA for myself and open an ordinary cash ISA for a friend/sibling and pay into their ISA, wait till I am ready to buy my house, withdraw my money from the HtB ISA to receive the government's bonus and the additional rate and then ask the said partner to withdraw my money from their account and hand it to me? This way I would be able to take advantage of the additional rate on the HtB accounts but am also able to invest the rest of my saving in another ISA.
Is there any legal problem with this scenario?
And if there isn't, what is the motivation for the banks to disallow split ISAs if it can be bypassed in this way?