I would say maple is a bad choice, long term, for a fretless fingerboard. Unfinished maple is highly susceptible to rot and decay--that's why it's finished even as a neck/fretboard wood, unlike rosewood, ebony, etc.
Any fretboard wood is going to wear down a bit from extended playing, but with maple you will be wearing down the existing finish on the maple fingerboard (which may happen rather quickly), and then exposing the raw maple to the elements of your hands, strings, and nature...it's not the ideal situation in my opinion. Likewise, the strings will wear away the existing finish and it will wear unevenly in time, which will affect the playability, potentially causing some areas to buzz etc.
Also, if the frets are simply pulled out, you will have some degree of unevenness in the fretboard, but those slots are unlikely to have any finishing beneath where the frets were, so you are exposing additional area of unfinished maple that rot and decay will happen. If you play it a lot, the fingerboard may need a major overhaul or replacement in time.
However, you said this guitar is gathering dust. If you don't care for the instrument, it may be a decent instrument to try out fretless, knowing that it will likely not be a well-tuned instrument (as is ideally especially with fretless in regard to the fingerboard and setup), and not a long term solution for playing, but a very rough place for testing. This can be okay, but without a good setup, fretboard, etc, it will be a lot like learning to playing guitar on an instrument that has the strings 1cm away from the frets--hard to learn on and play on due to the instrument making things harder than they already are.
You will definitely want a nut that is setup for playing fretless, whether you do it yourself to precision or have it done for you. You'd also want to have all the saddles adjusted for the fretless setup as well, which many do themselves but some are not comfortable doing.
Sometimes it's sad being a lefty...