The only quibble I'd have is that while it's easy to move money between them and an external 'linked' account (both ways) to move money from their TFSA account to another Alterna account apparently requires a phone call.

I guess it's no big deal and I understand that a TFSA withdrawal means you can only 'replace' it the following year if you are at your tax free limit.

But you may be nowhere near your limit or you may be well aware of the rule. Why not just have ticking a box to say you understand the ramifications, tax-wise, of your withdrawal and allow a simple on line transfer as with the other accounts?