Why not- Go for it I made the project for some yars ago now and it was a succes
Its correct that it will be a bad idea to use the original unit from BeoVox, becouse they are only tweeters and not fullrange. Make instead a diagram, remove the old units and keep them in a box to some day you want to sell them or replace the units you have change.
Buy some used/second hand but still good sounding PC units from Locitech or others ( with separate subwoofer) Control that the have the right sixe and space as new units!
Remove the old units in BeoVox 2500 and put the new full range speakers in with some kind of a adapter;
Bee very carefull Do not break the old BeoVox 2500. Bee very genle, becouse the original paint will fall off very easy
The adapter: Make a hole in the right unit size in a wheel of wood that have the size that match the hole in BeoVox and put everything together.
Maybee you can pay someone to help you with the adapter. that cheap, easy and the best.
Use glue that you can remove again... Paint with black - you can see everything behind the grill..
For one BeoVox 2500 I used two "passive" units (I removede the magnet) and two units with normal magnet and the last two holes was just closed .
I was using units from three pair of Logitech PC set.
It was proberly a little overkill, and the sound was ... But the project was very fun .
As PC speakers today im using the great Logitech Z-10 speakers These are one of the best sounding PC speakers that is made for music today I think that only a pair of BeoLab will sound better.
Modified BeoVox 2500 as modern PC speakers
If I should do the same project again, I think that I only will use one (or maybe two) good sounding units; one looking forwards/up (and only if there still are space; one looking behind,- the problem will bee the the size of the magnet) and all the rest of the holes should be closed. Then there is room and space for the unit to work correct.
That together with a good subwoofer will do it. Use it for PC, mp3 player, in kitchen, bedroom or..
But make it for fun - not for the sound...
Job done!