After a lengthy discussion with DisguisedAsBen, I believe we don't exactly need to replace 1 and 2, Short and Long white sleeves.
The conclusion I came to, is that upgrading to the newer LBVs as shown in that photo would be beneficial for the suggestion, as not only would it differentiate RTPC from response (in the absence of a hat), but also be in line with what the MPS are doing with modernising vests for Roads policing.
The second point that I came to is agreeing with BenWC on having a separate Fleece under vest uniform (perhaps for RAPTOR since HVs are apparently a big nono), maintaining their discretion with an all-black uniform but providing some insulation and then also providing a differentiation if TPAC uniforms were to get the same current RAPTOR vest.
I would like to point out, I do not think this is crucial, or quite frankly a very needed suggestion at all and I will remain with a downvote, however as an avid forum dweller I decided to throw my 2 cents into the pile as food for thought for anyone lurking and reading these suggestions who may agree with it themselves.
And finally, addressing the point of ERT getting the short-sleeved white shirt. This might be a very silly or quite a niece take from me, however, I see the short-sleeved white shirt and tie as a reward of sorts. The way I see it is that not only do you go through a gruelling application and interview process, if you're successful into RTPC as a division you then have to go through lengthy training and then another 2-week probationary period. After all that, you get the privilege of wearing the sought-after short-sleeved shirt with pride. At least that's how I saw it, as ERT I saw that short-sleeved shirt as a reward for those getting into one of the most prestigious divisions on the server, and when I did get in, I could wear it knowing I earned it.