I understand that spacers are not a solution to adding weight to the front (bumper, winch, etc) and they are really just meant to reduce the front end rake. The spacers do not affect the performance of the suspension. So if you add a bumper to the front and keep the OEM springs (which is my current situation), handing will be worse and so will the rake.
That said, the only downside I see to adding the spacers to the OEM struts is cost, time and effort. Adding the spacers will still improve the rake in the same way as they would w/o a heavy bumper. You would get better front tire clearance and look while parked but the suspension travel would still be the same. If you bottom out because the spring rate can't absorb the bump, it will be the same with or without the spacer. The spacer might prevent a wheel rub if you are running a larger than stock tire but that would be it.
So, unless there is something I'm not seeing here (and there certainly could be as I am no suspension expert), if you are staging your mods/upgrades and put the bumper on first, and you are willing to spend the money or take the time to install spacers to make your rig just look better until you can put the upgraded suspension on, then I don't see the harm.
Now if adding spacers to a LC with heavy front bumper and stock OEM suspension is somehow less safe than the same situation w/o the spacers, it shouldn't be done. Sacrificing safety for looks would be stupid. As I am really thinking about adding the spacers as an aesthetic improvement over what I currently have until I can pull the trigger on a BP-51 or something, I would appreciate any comments if my logic is flawed.