Is it taboo to mod a speaker?

Moding speakers is always something(like anything else), that you can try, indeed. You just have to do "one thing at a time", and see what you've got when you do a modification! If it works, you leave it. If it doesn't, you sould probably change it back!
I've rewired speakers, "braced" cabinets", changed drivers, and changed "single post" speaker designs into "dual post/bi-wire/bi-amp" capable speakers...but never change crossovers. The results are sometimes improvements, but some times not!
In general, if you're not a speaker designer per se, you can only cross your fingers. But, you try and see, and then you'll know for sure!
Good luck

I have bought some audioquest cable and replaced wire.I think the designer did his or her best and is best left alone.It reminds me of wisdom . if you are looking to change something,you may well find it somewhere else and sell your speakers unmodified for a good price

I'd add, glue on felt ring around the tweeter, plug port if too much bass, in addition to Zaikesman's excellent post.

...And of course, I think we've forgotten to mention the #1 speaker mod of all time - listening with the grilles removed.

Upgrading the caps in the tweeter's filter will greatly help some speakers. Some folks think this is the most important passive component in the entire system. Change with a like value.

You can go to forums like the Madisound and it is likely that someone has experience with your speaker or one like it.

I remain,