If you effectively do a Roth conversion, with the 401k withdrawal amount equal to the Roth contribution, and not penalized, and taxes paid using some other already taxed source, then it's a little strange, but not crazy. You might be able to do a straight up Roth conversion and not worry about contribution limits and penalties. Or do a full or partial 401k to tIRA rollover and then do a simple tIRA to Roth conversion.
Withdrawing from the 401k, paying taxes, and contributing remainder to the Roth account is sort of a neutral transaction if your tax rates will stay the same now and throughout retirement. The Roth normally has a slight edge in this case because it can store more after-tax value per contribution than the tIRA. If the after-tax value is the same for each, then they are virtually equivalent.
As long as your earned income covers the Roth contributions you may contribute for both you and your wife.