It looks like a nice, light-weight day jacket. Probably cooler than tweed, even if it is wool. I wouldn't worry about the length. It's already made to be worn with a kilt.
Just my two cents here:

The No. 2 Dress tunic is just that -- a dress tunic for the parade ground. It is cut like a dress uniform (again, think USMC "greens" or Army Class A's) and is not as comfortable as a civilian kilt jacket. And since it is similar to the US NPS service dress jacket (our dress uniform), I can attest to the fact that they get pretty warm, especially in the summer. It's really not a practical garment for "kicking around" in, because it's not designed to be.

But, it's your decision, David. And at least it would be going to a "kiltie".

Cheers,

Todd