I don't know how the Titanic kit goes together so can only offer some practical suggestions based on converting the big Revell Queen Mary 2 kit which is of a similar size.
Obviously you need to get into the middle of the model and almost certainly the best way to do this will be to make the boat deck removable from behind the bridge. This might entail running some extra plastic support on the inside of the superstructure for it to sit on and enable it to be screwed or bolted down.
You will also need occasional access to the rudder head as if you damage the rudder and everything is welded up you won't be able to easily make repairs so the poop should be detatchable but normally screwed dowm.
There may not be much room around the rudder head so you will need to think about how you are going to operate it. A small servo might fit under the poop near the rudder otherwise you might need to consider mounting the servo under the boat deck and operating the rudder with either a rod (possibly bent to pass under the aft well deck) of by using a flexible sheathed cable as used in model aircraft. It all depends on how much room there is.
Although the boat deck should be made detachable, ideally you don't want to remove it at the pondside or you will inevitably break things off so concealed remote master switches should be used to avoid the need for this. There are various options including magnetic switches to do the job. Despite this on my QM2 I have knocked something off every time I've taken it to the pond. Those delicate platic fittings are, well, delicate!
Although the hull looks quite big you will almost certainly find he the model is tender. Firstly because it is narrow for its length and secondly all those plastic fittings carried high up are actually relatively heavy and there is little scope for cutting away covered sections of deck under the superstructure houses to make much difference to the weight.
If I were you I would make provision for fitting a false keel, prefereably detchable. My QM2 did stay upright in the bath with just internal ballast but the slightest breath of wind laid her right over due to the high superstructure. A small weight on a deep keel works better than a heavier one stuck directly underneath the hull as the model doesn't then bob about unrealistically. Despite doing this on my QM2 the model is still unhappy in anything more than a gentle breeze.
Colin
Edited By Colin Bishop on 13/05/2020 10:24:05