It's already been, as far as I know, especially for Nextel devices.
Things like Installing third party web browsers such as www.reqwireless.com
should work for your Nextel, as well as installing Verichat from www.verichat.com
should work too.
Most "BES" networking software will work on your Nextel without BES. No BES/MDS needed.
You may need to upgrade to BlackBerryOS Version 4.
More information in "BlackBerry FAQ" link below: