I think some of the confusion is some folk missing the point that the op was planning on putting his accumulator tank downstream from the hot water heater, because of proximity of the heater to the pump. I tend to agree with all those who said this is probably not a good idea. There seems to be unanimity that it can go anywhere in the cold side of the circuit, but best near the pump, even if a T junction and a length of flexible pipe is needed to place it somewhere convenient. I find it hard to believe the OP's water heater is so close to the pump he cannot do that.
PS. Sorry, just re-read his post - he is referring to the T, and not the tank, so yes, if in the cold circuit, even tho the hot comes off close to & before it, the hot water would not flow through it, so it would be ok done that way, as it would still work to prevent hunting of the pump, even when drawing just hot water.