Upgrading 9spd Allez to 105
You don't necessarily need a new wheel. Some larger 11 speed cassettes can fit on a 10 speed road freehub body, as the larger sprockets allow a wider spider that can overhang the inboard end of the freehub body. A 105 GS derailleur max small sprocket is 34 teeth, but that can very likely be pushed to 36.

There should be no compatibility issues. On a 2007 bike you presumably have a threaded bottom bracket shell and external bearings. R7000 cranks still work with that. You'll have 130mm rear hub spacing, that's not a problem for chainline with R7000 cranks.

Here's the potential gotcha: cost relative to a whole new bike. Add up the cost of a 105 rim brake groupset bundle, new wheels, tires, all the miscellaneous bits you should replace at the same time (cables, housing, bar tape, tubes ...) and the special tools you'll need (BB tool, chain whip ...) and you may find that's a very significant part of the cost of a new 105 equipped, alloy framed bike. Remember with a new bike you get better comfort, modern geometry, ability to run wider tires etc.

That said though, it's worth looking at the used market for wheels. With the switch to disc brakes there are deals to be had on highish end rim brake wheels.