Medium Blazers are definitely a possibility; My usual go to is 2 tons, 2 slots, 6 heat, 8 damage , 3/6/9 range. Gives them an "Inner Sphere Heavy Laser" feel.
(Small Blazers are pointless though, those just end up being a Medium Laser But Worse after rounding.)
Chemical Blazer would of course be still 9 tons/4 slots, 12 damage at 5/10/15 range, but would only generate 12 heat. Ammo is the real point of contention; you could either go with 5 (half that of the Large Chemical Laser) or 6 (80÷12) depending on how efficient you want to imply the design is.
Similarly, a Medium Chemical Blazer (or, as I prefer, a Light Blazer, since the small laser is pretty useless for that) would be a debate between 15 and 18 shots per ton.
Instead of a second shot at +1, I'd probably go for a roll on the 2-column of the cluster table. It would also reduce the thresholding to the damage of a single core.
I am not in favor of using the 2 column overly often; in
most cases my preference is to make two To-Hit rolls (with or without a modification or special rules about hitting single locations) as this involves the same number of rolls for most things. In point of fact, I prefer to use it only for missile weapons and RAC type repeaters that can get other columns if desired.