Thanks for all the suggestions, Astrobe! This is just the type of help I need with this OXP - fine-tuning all the possibilities.
And apologies for this long post. It started small and then inexplicably grew... weird.
For the next version I've put a tech level factor into prices, so items should be more expensive at low tech worlds, and cheaper at high-tech ones. There's probably more I can do with this, varying prices based on random or other trade factors, but I think what I've put in now should work for the moment. I've also removed the equipment space factor for escape pods - you're right, these shouldn't use up equipment space (for logical reasons as well - an escape pod wouldn't be fitted into an equipment rack as there would be a special spot in the ship's structure that would be designed to take a pod).
First, make "trader" variants for some equipment.
It might also be valuable working out what equipment would be essential for a trader, and then determining if the space each equipment item consumes needs to be adjusted, or if the total equipment space in that ship needs expanding. I've been fooling around in a Cobra Mark I recently, which admittedly is not a proper trading ship, and I've already used up all the allocated equipment space and I still don't have shield boosters. Trader ships are typically ships with larger mass, and should have considerable equipment space to play with (a Boa has 30t, a BCC has 35t, an Anaconda has 40t). If a large trading vessel (ie greater than 100t cargo space) has a low amount of equipment space, it might be better to add a ship-based equipment space exception than micro-managing the equipment items themselves. As the poet says, "There's more than one way to remove the epidermis, dermis and subcutaneous fat from Felis catus".
In any case, I've added extra variations for engines, thrusters, and energy. The new versions (a) cost twice as much as the original versions, (b) take up half the space, and (c) contribute towards cabin heat. Hopefully that will calm the trader spirit! My reasoning for leaving out the other parts:
- The only difference in the performance values for these are how long it takes to spin up. I've added some variability to the heat generated for the next version, though.
- These are kind of a luxury item anyway.
- I'm hesitant to do much more with shields, as getting it to work with the core shield boosters and mil shield enhancement, ignoring other OXP shield equipment (Equalisers in particular), is complex. I've tried to leave existing equipment as-is as much as possible, so I've avoided playing with the shield recharge rate, leaving it to the shield boosters and mil enhancement. That being said, there may be a case for diving into this again.
- With the reduction in space with the last update I feel like these are at the right level for everyone, but if you have some additional configurations you'd like to see I'll certainly look at including them. At the moment their heat generation is directly linked to their burn rate (cheaper injectors = faster heat buildup). I would probably need to de-couple the calculation from using burn rate to using an ad-hoc value stored in the script_info.
- I don't think there's a lot to be done with these.
- Armour is something of a luxury item, so I don't think much needs to be done here.
- Changes in one of the other areas may lead to changes here, but again I don't think much can be added.
If you think there's more scope for adjustment in one of these sections let me know.
 extensions and perhaps some pieces of equipment incur cabin temp penalties, but it doesn't appear in the stats overview.
It's kind of hard to do a "predicted temp" value, as most of the items that have a heat-related value only cause that when they are used (eg hyperdrive, injectors), and the amount of heat shielding the ship has also comes into play. I'll continue to think about how to best represent the data to the player, but to my mind there might be need for another screen entirely where the equipment items that generate heat when in use are displayed, and the reason for a base-level increase to heat can also be shown (eg bus overload, equipment space extensions). The other factor here is dealing with 3rd party OXP's that want to hook into the heat calculations. For this screen to accurately reflect what will generate heat some form of interface will be required, which complicates the hook process somewhat.
Anyway, I'm going bed down the current changes and try to get an update out later this week, time permitting.