Re: Stop poking me with that stick!
Taking the bottom heads off is an option but one I wouldn't necessarily encourage for two reasons:
i) The 'warping' that you talk about. It is unlikely with modern drums but still a possibility. More to the point though, that if there is any contact with hard surfaces you can ruin the bearing edge at the bottom of the shell and that will make tuning very difficult (think of it in terms of the bridge on a guitar - if it's damaged, it's not staying in tune).
ii) Hardware rattling. Drums that are designed for only one head ('concert toms') don't have any hardware on the bottom half of the shell. When the head is taken off, various parts can come loose and rattle noticeably during playing.
With the choice of heads - hydraulics are an archaic option. There is an element of taste here and obviously tastes change with time but the general advice now is that a less-dampened and more 'natural' head will give you more tone, volume and projection. Modern taste is very much towards a more 'natural' sound. The era of 'dead' drums sounding contemporary is - with respect - in the past. That's not to say you can't put hydraulics on or even that you shouldn't it's just something to bear in mind. Also, putting those heads on will significantly reduce the volume of the drums.
You're probably better off going for a two-ply head like an Evans G2. They will give you a lot of options and are just as hard-wearing as any hydraulic head. They'll give you more tone, volume and projection.
As for tuning? Look up 'Bob Gatzen' on YouTube and marvel at the wonder that is free information!