Can several tehorim make themselves tumoh in order to be mezakeh the rest of the teme'im to bring the Korbon Pesach by reducing the deficit of teme'im and create a majority of teme'im....
Would such an action be considered as a Mitzvoh Haboh be'aveiroh or because the original group of teme'im did nothing the MHB is irrelevant
Sholem, UK
There is no prohibition against a Yisrael making himself tamei. See Rambam Hilchot Tumat Ochlin 16:9:-
" It is permiited for a person to touch any of the tumot and become tamei; since the Torah only warned the sons of Aharon (the Cohanim) and a Nazir not to become tamei to a dead body, which suggests that for all of the people this is permitted".
KOL TUV
Dovid Bloom
Additional point:
However the Gemara below 80a states that according to Rav, if half of them are tahor and half of them are tamei, we make one of them tamei by making him touch a tamei insect, because if we would make him touch a dead body he would not be able to bring the Korban Chagigah. We try to make him tamei in a way that will cause him to miss as few Mitzvot as possible.
Behatzlachah
Dovid Bloom