Blockland is already running a heavily modified version of the engine to the point where you can't really call it less updated than newer versions of TGE. Improvements and patches that were backwards compatible with the old engine and were needed were added. TGEA isn't necessarily an upgrade, it's a jump from one totally different engine to another.
People suggest switching the engine all the time without any really great reasons. If there's something from another engine you want in Blockland, suggest it. Badspot has the source code to the existing engine. Given enough typewriters, monkeys, and time he could add whatever feature you could possibly want to the engine. If it's Collada model support you want, or multiple terrain blocks, fancier physics, some funny language interpreter, suggest it, instead of saying "switch to the portal engine so i can play with portals."