Thank you for the reply, we can discuss about two different parameters.
1. The size of ship models, what you see and enemies try to hit in the deep space.
A feature of fighters is the extremely small size, so far very few ships provided such hard to hit and laser equipped targets, like combat drones
(the leftmost model in the first row in the last image above). I think the small size is a good thing here, give a feeling about how hard to catch these with the weapons of a much larger ship.
The last image show possible larger fighters which are less hard targets but survive more hits. Even five different fighters are imaginable after a while, but I plan to use existing ships only, this is why I gathered the candidates.
I can adjust the sizes of ships so if you have suggestions about sizes or to use another models then just tell me.
2. The occupied space in cargo bay.
This is a playability question, so regardless of a light figther fit into a cargo canister, it occupy more than 1t space in cargo bay. For handwavium repairs need additional tools with supply and the pilot and service team need some living space.
Moreover somehow must limit the numbers to prevent oddities like 100 fighters in a Python. The maximal number is a way for this, but if only 8 is allowed and these occupy 8*1t only then this mean almost nothing in a freighter, so the smallest fighter should occupy more than 1t.
If you would like five different fighters then 5, 10, 15, 20 and 25t is a line where 8 allowed fighters still force to make decisions in most freighters, for example can not fit 8 of the largest fighters into the 175t cargo space in a Boa Class Cruiser.
I like to hear suggestions, even more fighters and lower occupied spaces are imaginable.