Hmm, not really an answer to your question... but are you really rebooting 10 times a day?   

File > Random boot screen at startup.

Bleh, nevermind...missed the bit about selecting which ones to use randomly.

well you could create a folder inside the same folder where all the other bootskins are located, move the ones that you don't want to use into this folder and leave the 10 bootskins you do want to use as is in the original folders, select random bootscreen at startup and voila, you've manually recreated the same function that have with logonxp.

Yes this is a very manual solution but sometimes when the software at hand doesn't provide the functionality you need, you have to find a way of making it do what you want.

I actually do something similar to this, I've created a !retired folder in the skins folder where the bootskin folders are located, I move the one that I've downloaded but never use anymore into that folder (just in case I want to use them again at another date instead of downloading them over again).