There's not a reason given why someone must set the ion pod up at the time of a storm -- why it shouldn't be ready to go at any time, like other probes.
We don't have any evidence that other probes would be "ready to go", either. Even Picard often has to call for a probe to be prepared, rather than simply launched.
It all makes good sense if we view it as a parallel to today's tornado hunting. You never know when your elusive subject or study will appear, so you can't stay in constant readiness. Your instrument has a limited lifetime, so you only fire it up just before hitting the phenomenon. And your driver is at least as important to the results as your instrument operator - it's up to him or her to drive the truck right onto the path of the tornado at the exact right time, using his or her best judgement, and to be in command of the deployment sequence, a finger figuratively (or sometimes literally) on the trigger button.
And I'm not ready to dismiss the non-canon written reason of the pod being a danger to the ship; that's pretty good evidence.
I'd dismiss it outright. If the pod is a grave danger to the ship, Kirk would simply refuse to use it.
We've never heard of shields being disrupted by a geometry change in the ship's outline (say, when sections are blown off in battle), so that's automatically out. Keeping the shields down so that they don't disrupt the instruments... Kirk wouldn't do that in a situation amounting to a yellow alert, and in any case it would not offer any rationale for the need to jettison the pod. If the instruments don't like shields, screw them - if need be, fry
them when the shields must be raised. Or just shut them down.
So evidently, the pod wasn't simply being readied to take readings; ion readings were actually in progress.
Sure. But that's what would happen if the pod were
being readied, too. The officer rushes to the pod, starts firing up the experiments; some of them start whirring and beeping; the officer informs the CO that he's achieved a milestone but isn't ready yet; and the CO tells him to make it fast and give the final A-OK so that the thing can finally be launched.
What I'm still not in favor of is the light being the ion pod. Not nearly big enough.
I'd argue here that the pod would be inserted deep within the hull, with only a sensor head (or possible porthole) showing. In fact, several such coffin-sized devices might be housed there, beneath the hangar deck and ready to deploy sidewise. These would indeed perform a variety of functions - but none would be big enough to be multifunctional by itself. Instead, there'd be a spectrum of the things.
For example, the operator would crawl into the thin cylinder, kick free of the ship, and deploy multiple arms from this heavy duty spacesuit, in order to begin repairs on the exterior... An eminently logical tool for starships, and quite familiar from 1930s-50s scifi comics. One wouldn't enter it vertically, because climbing into a thin cylinder from the top or bottom is awfully clumsy. Sliding into it horizontally from the bottom would be much easier.
The ion pod would simply be a variant of this repair pod, packed with instrumentation that can be operated on both attached and deployed mode. And like T'Girl
says, it would be modern instrumentation, stuff that hasn't yet been integrated to the old mothership, and thus e.g. requires an expert to activate. Modern instrumentation in a modular plug-in package - what could be more logical?
There's also the issue of reloading the pod after use (without having to go outside the ship). Rather than have a section of the ships who's sole purpose is to prep and jettison ion pods (a rare need) it makes much more sense to have a multi-role system.
The repair pods would fly themselves back without need for outside help. The ion pod would be a throwaway item if used on detached mode. (It probably also typically gets destroyed soon after deployment, since no attempt was made to locate the pod in the hopes of finding Finney inside...) Reloading might not be an issue simply because a starship won't be able to afford multiple pods. It's not as if submarines today carry spare ICBMs, either.
And it would make more sense to provide dedicated berths for the repair pods than to launch them from the shuttlebay. Deploying a single-man pod doesn't require any of the facilities of the shuttlebay, and it would be awfully wasteful to pump all that air and open those heavy doors for no good reason. OTOH, placing the array of repair pod berths right next to the shuttlebay (or, rather, the hangar deck below) would also place the pods ideally next to auxiliary craft repair facilities, spacewalk gear stowage, etc.
I believe aridas sofia
introduced repair pods in this very location in his TOS ship blueprints, although he used variants based on Jeffries doodles, rather than the simple narrow cylinder that would best fit the supposed ion pod berth.
Finally, here's the supposed reloading of the ion pod in the TOS-R episode:
Replace the simple dome with a cylinder capped by said dome, and you have a perfectly practical small spacecraft to be used as a repair pod... I'd like to postulate that the corresponding (and unseen) portside location features two pod berths, rather than a berth and a porthole, and routinely carries two repair pods.