With timing problem you mean those units would be produced too early or what?? and what do you mean with medium vehicles come too late? These changes would´nt delay anything
If you keep current T1 unlock costs, comet and churchill arrive too quickly, creating situations of old OKW, where we had 12 min T34 vs 14 min panther, except now it would be P4 vs comet.
If you keep current anvil/hammer costs, there is NO point to ever get the upgrade, because it would leave you extremely far behind the tech to the point where early med tank would obliterate you and neither, bofors or aec would be even considered an optimal choice, removing both from the game and destroying brits teching as a whole.
Basically, whatever you do-it does not work as it either makes brits extremely OP or extremely UP.