Chris,

If you can visualise the type of ideal
pin joint I'm talking about, the horizontal component of the tension is
not applied to the column at all. It is transmitted around the column
through the joint.

That is not at all what you drew. If you intend to transfer only a
vertical force to the top of the beam, you are going to need a slot or
horizontal roller on top of the beam, with the likely outcome being a
statically indeterminate problem or something that leads to a
contradiction because it is not adequately supported.

Bill