Using an addon to rewrite xml files?

I’m trying to create a system where users can choose how to speed up my animations and window transitions. I know you can speed up animations in the addon.xml using the ‘effectsslowdown’ tag, but I think this is a bit of a hack and would be over-written every update anyway.

So I’ve created two speed profiles currently using two sets of Constants, one ‘default’ and one ‘quick’. The transitions and animation times are all multipliers of a base time. What I’d like to do is change the ‘quick’ profile to a ‘user-defined’ profile by letting the user enter a value e.g. 200 and then that will be used as the base time and then the other constants would be calculated from that.

Is it considered bad form or inadvisable to do this by using a python script to overwrite the values in my Constants.xml file? I am assuming this would even be possible with something like ElementTree, although I’ve not actually looked into the specifics yet. Just wanted to get a sense of if this is a direction I want to go down?