That is a great project.Except I have absolutely different idea of "entry level".I see it rather as super mega fancy workbench.
Get yourself a trailer, get a new car and put an old one onto the trailer behind you as a source of spares.
Asking the real questions.
Unfortunately, zippers on the luggage are relatively easily open without even using it's pull and closed without leaving much visible mark. The method needs some practice, but is totally workable.
According to physics the larger the balloon the more efficient it is. Surface area/volume ratio marks how well it flies.In case of cylindrical shape of constant diameter, the longer the better. Though a very long wiener would bend and wobble.
I am sure, to harden a knife blade you would need much more powerful device. As this one just heats part of the nail red. But the scheme can be rather easily scaled up to pretty much any power.
Are you sure about pricing?According to Microchip MEGA8-16PU costs 2.41 per piece, ATTINY85-20PU is 1.20Never mind, ebay offers mega for .99 and tiny for 1.11 :)Though mega won't come in DIP8 package, if size does matter.
Even tough there are other solutions, ATtiny chips still do have their charm.Affordable, compact, wide powering options, potentially very low power consumption, have good community behind, are both reasonably compact and quite simple for uninexperienced DIYers. So if you need something that uses just couple of pins and lasts for years off battery, ATtiny is still way to go.
Great idea. Though drill press is not intended to carry radial loads, shaft bearings might say goodbye after some while. So in long term it would be wise to get yourself a drum sander.