Anyhow, it seems clear that there are several methods when dealing with seized spindles. One involves using a power drill, another blunt force, another involves a specialised tool to help re-align the platter/bearing bundle. I decided to use a stylus from my old Palm Vx. It seemed to work well and I was at least able to get my drive spinning relatively freely again. The next problem that I faced was head/servo movement. I checked my re-assembly several times and everything seemed to be in check. However, after careful examination I realised that a cable that led from the controller board to the head was deformed/broken which meant that power could not be sent to an electromagnet at the end of the head assembly which is ultimately used to control head alignment over the disc platters. After re-alignment head movement seemed to be back. While its clear what the problem is, I'm not sure how much further I can push this with my existing equipment. The connections/wires that need to be fixed are basically the size of pin heads. It will take a microscope and a bit of luck to be able to accurately re-connect the relevant connections.
Moreover, unlike previously where switching parts seemed to be quite simple I'm discovering that drive recovery nowadays is far more evolved than it used to be. While some parts are interchageable others aren't so easy. Based on some research it seems as though some drives may have begun to place part or all of the firmware on the actual drive itself which makes parts transfer not so simple. The firmware from the old drive needs to be extracted or procured from another location (can be trivial or extremely difficult depending on the situation/manufacturer as some publish tools/software to do precisely this while others rarely publish any supporting documentation/software at all).
I suspect the best/simplest method may be sourcing another drive for its head assembly (if you don't have specialised head removal tools you're best choice is turning the drive upside down and pushing it towards the back wall of the drive enclosure to remove it and enhance your chances of removing it without causing significant drive damage)(Obviously, you've discovered by now that you can often get by without having to resort to specialised tools a lot of the time. However, like general 'tradesman' it is far easier if you have them and you need to take extra care if you don't have them.). I'd like to know whether they alter drive heads based on drive density though? Clearly, when switching from single to multi-platter configurations this will be the case. How about switching from a single platter discs of different density though? Surely, efficiencies in mass production should mean that you use the same heads while altering only the platters, firmware, controller card, etc?
As an aside I've noticed a lot of good deals for SSDs of late. However, it's also clear that some of the drives on offer have a history of data loss as a result of dodgy controllers, firmware, etc... For the moment, I would do my homework before purchasing an SSD, hold off on the technology while it matures, and/or just use it for non-critical/read only purposes.
A word of note, if you're working with this type of equipment you should primarily be thinking about the most minimal way to get things going again rather than seeking the most elegant solution out there (at least initially). I recall working an phone that had sufferred from water damage. Everything seemed to be fine but the power switch needed to be replaced. While I managed to find a replacement from Jaycar I tried to get too cute with the repair and ended up damaging the replacement switch. Luckily, the switch was only 95 cents and the phone was relatively inexpensive.