I think this is the answer:
ENGINE HOMOLOGATION
1. A homologated engine is an engine identical in every respect to either :
blah, blah, blah...
(iii) An engine delivered to the FIA after 1 March 2007, or modified and re-delivered to the FIA after 1 March 2007, which the FIA is satisfied, in its absolute discretion and after full consultation with all other suppliers of engines for the Championship, could fairly and equitably be allowed to compete with other homologated engines.
blah, blah, blah
3. The FIA, in consultation with the TWG and the engine suppliers, will from time to time issue indicative information as to the tests and inspection procedures to be applied.
So, you can submit a new engine and the Technical Working Group at FIA will tell you if you can compete with it.
About "someone, stupid enough... to enter F1 in 2010", well, "to hope is to contradict the future".