I disagree that it will make LF's obsolete. They travel at 475 and can truly intercept - if HF's have 400 speed and a VHF has 375, it does take quite some time to catch up to the VHF is he's a few K's ahead. It's the same speed difference (25) you get between a transport and a VHF, and that isn't all that amazing tbh.
Not sure what to say about LF's - not sure if balance is finished. BUT, that being said, they are at the moment glass cannons (as you can still get 2.0 refire 3000 dps guns) and fill out their own role at the moment, besides from just interception (which this change won't make them worse at), and I don't see HF's really threatening that.
The majority of people that pilot a light fighter just do it with the intention to whizz around and annoy, and not with the intention to actually kill something, and I don't think this proposed HF change would have a real impact on those players that choose LF's so they can dodge all day.