Because there are no special construction advantages to not having an engine on a military station, you might want to put a small commercial engine on them so they can put themselves in position slowly or take themselves back from a jump point to a colony for refitting, and also so they can use commercial jump tenders, since they might be too large for your military jump drives to handle. Then you have something like a pre-WW2 coastal defense ship, which makes a lot of sense as a pure colony defender. Something like that packed full of weaponry has probably one of the best PPV/tonnage ratios you'll be able to build, too.
There are some other things I recently discovered the hard way about basing fighters on planets - you need to make sure your colony-based fighters have enough onboard MSP capacity to cover a max repair, otherwise they might break their most expensive part (probably the engine) and not be repairable without a ship-based military hangar, which you probably don't want to keep idle at an outlying colony. The fighter design in the OP has that issue - if you're building them before any building carriers, they might break in a way that can't be fixed, especially if you're training them. One fighter maintenance storage bay is probably all you need to avoid that.
If you intend to train colony-based fighters at all, you'll run into serious issues with deployment time, too - their clock will increase at double speed unless they're inside a military hangar, and bad morale will ruin their training speed and cause other problems, so either you need to ratchet up their deployment times and frequently cycle them in and out of your training NAC (don't do this, it's micromanagement hell) or only train them on carriers/fighter bases. Apparently repair facilities and R&R for fighter crews in training are available on warships but not on planetside bases?
Then if you build a fighter training base, make sure it has plenty of deployment time and fuel capacity even if it doesn't have an engine and never leaves orbit, and give it a standing order to refuel when it gets low, since fighters will burn lots of fuel while training even inside of a hangar. I haven't tried it yet but I think it might also potentially make sense to build trainer versions of fighters with super-long deployment times and high efficiency engines, train your fighter crews on those, and then refit them into combat models at a minimum-size military shipyard. It might be impossible to refit the engines on most fighters, though.
After your fighter squadron is done training, you can then use a commercial fighter transport to drop them off at a colony. But first make sure you have enough maintenance facilities for them and also probably stocks of duranium, uridium, and gallicite so those facilities can produce MSP. They'll also need some stocks of fuel and replacement ordnance as well as a cargo shuttle station, ordnance transfer station, and refueling station, if you don't have a spaceport, which you probably shouldn't at a small outlying colony.
Basing fighters directly on colonies requires a lot of infrastructure on the ground compared to having them on bases in orbit above those colonies, which can have long deployment clocks and large onboard stocks of fuel/MSP/ordnance and can be periodically resupplied and overhauled by visiting support ships. But if you have that infrastructure anyway, you can save resources and keep your fighters arguably somewhat safer by cutting out the base and putting the fighters on the planet. It's also good to be able to support fighters directly on a planet because that lets you use ground support fighters as well. You'll probably have ground forces on your colonies before you put any defenses in orbit around them because they don't require the same kind of enormous chains of logistical support, so ground support fighters should always have something to assist.
If you have STOs with PD weapons and long-range beams, fighters with AMMs and ASMs, and adequate ground forces to protect your STOs during an invasion, you can have a pretty tough colony with a complete set of layered defenses and nothing sitting vulnerable in orbit without it costing much in mineral upkeep. An enemy would either have to destroy the planet through mass bombardment through your PD and AMMs or land a large number of troops under fire to seize the planet.