If Heseltine takes it, then there is not the slightest chance that Howe would return. Maybe, maybe if someone from the right gets it, but not Heseltine. The party and the country will want unity at this point; Heseltine would already be bad enough for the right, bringing back Howe would be a red rag to a bull.
Redwood, Hague, are too junior at this point. Redwood much to so for Northern Ireland, especially in these circumstances. (I don't think Hague was even a minister at this point) I think on the whole, it will be mostly the same cabinet as before in order to preserve the idea of unity, with a very modest re-jigging. Brooke would probably be kept on at NI, or if not, Heseltine will probably elevate Mawhinney to the post - all the experience of the department needed, a 'safe pair of hands' and good unionist overtones. (Actually, Mawhinney makes more sense)
One thing that has to be considered here and which has been ignored is the role of resignations. This is a major security lapse. That probably means Baker (who was always regarded as a bit of a duffer anyway) resigns from the government, perhaps even some senior police/security figures as well. I agree with others in respect of post-9/11 counter-terrorism legislation coming in.