I agree with the concept of light weapons having a higher percentage of the total slots. 'Point defense' weaponry can tend to soak up a lot of weapon slots if you are trying to cover multiple arcs, depending on if you have a lot of seeking weapons, small craft, and such to deal with.
Also, in SFC, combining weapons into shared hardpoints has other consequences. I.E. 4 weapons in the same slot use only one unit of 'repair stores', same as a single weapon in the same hardpoint. Your implementation may handle this differently, of course.
In my mind having more than 2 weapons in a hardpoint reduces flexibility a slight bit as well... I'd rather have 20 hardpoints with a 2 weapon cap than 10 hardpoints with a 4 weapon cap, if the only reason for combining these is 'saving screen space'. Of course, if the weapons console 'window' is tiny, then having 40 hardpoints might look way too cluttered...
If you are talking a quad mount gun or something, then 4 weapons in that hardpoint might make sense. If we had 'WWII style turrets', then having 3 or even 4 heavy weapons in the same mount would make a certain amount of sense. Star Trek doesn't really do turrets though, just 'shared' mounts... and we don't have fine control over individual weapons in a hardpoint (i.e. we can only fire one at a time, or all of them, so if you wanted to fire two simultaneously, well that requires two keystrokes instead of one. Or if you only want to arm two of the four weapons, or mix overloads with standard loads, etc., well all weapons in the same hardpoint will share the same state, power limitations aside, so you lose 'fine control' by combining weapons in a hardpoint).
I think a 24/12 split is probably not a bad target. Pairs, triples, and quads are common, and 10 is just a weird number in that context (not divisible by 3or 4). Or 16/12, 18/12, etc.
'Shared location' multiple hardpoints can always be expressed with two touching boxes (i.e. the don't have to be separated), to help with the screen real estate. Similar to how they are done on SFB SSD's. Compromising a bit, of course, with allowing 2 weapons to share a hardpoint (i.e. 4 weapons in the same location expressed as two hardpoints of 2, again to allow addditional flexibility).
Another concept which is 'lost' in the translation from SFB to SFC is the size of heavy weapons. PPD's and Plasma R torps are larger than some of the other heavy weapons, so they might occupy 2,3, or 4 'slots' in a hardpoint. I.E. 3 or 4 Plasma F's might fit in the same space as a single R torp...
Also, SFB's 'one size fits all' concept for heavy weapons (plasmas aside) is a 'kludge' to keep things simple. In reality, you might have multiple sizes of disruptors, for example, which do more damage (and perhaps have longer range) as they grow in size. If you are making your own game, you can introduce some variability here in some cases. Plasma Torps in SFB/SFC are a good example of this concept in practice.